There are good -- even great -- phones you can't buy from Verizon, AT&T, T-Mobile and Sprint, no matter how hard you beg. The excellent OnePlus 6, which costs about half the price of the iPhone X, is one example. There's also the Huawei P20 Pro with three rear cameras, and the all-screen Oppo Find X and its astounding slide-up camera.
And while there's a larger online marketplace for phones than ever before, the truth of the matter is that most people in the US buy an iPhone, Samsung Galaxy or LG device directly from their carrier.
This mobile trinity is frustrating for adventurous types, especially when phone reviewers like me point out models that are worthy of your time and attention, but aren't available on a carrier. So, what gives? Why can't you get any Google, Motorola, Huawei, Xiaomi or Sony phone you want from any carrier you'd like?
The reasons are many, but it all boils down to the unique condition of the wireless industry in the US. Here's the simplified low-down on how it all works and where you can buy phones outside your carrier that will still play nice with your SIM card.
When you buy a phone from a carrier, you're getting a guarantee that your device meets a certain standard of quality across the board -- the data and cellular network connection, and also the hardware itself.
A carrier also provides services, like Wi-Fi calling and HD Voice, and shoulders the responsibility of customer support. If something's wrong with your phone, that's their problem. The phone you buy from a carrier is usually "locked" to their network, and in exchange, you can access all its services.
But an unlocked phone you buy from Amazon, Best Buy, NewEgg or Target doesn't hold those same guarantees. The same goes for buying directly from Apple, Google and Samsung's sites. You can still insert your own carrier's SIM card and be able to make calls and data services, as long as the wireless bands are compatible.
Just don't count on being able to use Wi-Fi calling or get grandfathered in to a cheaper service plan you've had for 10 years. And if something happens to the phone, that's your problem (or your manufacturer's, assuming the warranty holds), not Verizon's or AT&T's.
The Huawei P20 Pro is one of the best phones you can buy anywhere. It's just not available in the US. At the heart of it is the government's concern that China-based Huawei could spy on US citizens through Huawei's networking equipment.
Although Huawei and ZTE's phones had never been singled out before, it's speculated that this political pressure detonated AT&T's plan to carry an earlier phone, the Huawei Mate 10 Pro, and propelled Best Buy to stop selling new Huawei devices, which CNET was first to report.
You can still buy some, including the Mate 10 Pro, from sites like Amazon, but Huawei's future in the US is looking dead in the water, unless something changes on at least one side of the Pacific.
ZTE, meanwhile, is also in a strange limbo. In May, the US government banned ZTE for seven years after learning that company employees were involved with illegally shipping US equipment to North Korea and Iran. President Trump intervened, and now ZTE must pay $1.7 billion in penalties.
Not every company can sell 52 million units of a single phone in three months like Apple can, or make them fast enough even if they could.
One strategy for companies like OnePlus is to build a limited number of devices. If the phone sells out, no problem. That creates a spike in demand.
But carriers aren't interested in whipping up buyers' angst by depriving them of the object of their cellular desire. Carriers want to sell phones -- lots of them -- so they can keep customers hooked on monthly services. And if the brand in question can't produce enough volume to support that demand, that device isn't one that the network can promise to its millions of customers.
Carrier banding is one of those pain points you never have to think about when you buy your phone through a network.
Cell phones work because the cellular signal travels to and from the device and the networking equipment over radio waves. Each carrier has the right to use certain slices, or "bands" of the wireless spectrum.
Some bands are better at reaching indoors; and some are better at covering large territories. Regardless, if the phone you're trying to buy works with bands that are common in, say, China, but not with the US carrier you want to use, the phone won't work here.
To make matters more confusing, every phone in the US relies on one of two incompatible cellular technologies: GSM, which most of the rest of the world also uses, and CDMA, which you do find in select countries. Verizon, Sprint and their subsidiary networks (like Boost Mobile) use CDMA technology and bands, where AT&T, T-Mobile and their prepaid branches (like Cricket Wireless), use GSM.
While most modern 4G LTE phones -- even GSM versus CDMA -- have enough shared bands that they'll probably get some reception when traveling across networks, reliability will be anyone's guess. Further, other services -- such as voice calls -- could be unavailable in any given location.
So that flashy Vivo Nex that sells in Asia doesn't perfectly align with any carrier's 3G and 4G bands. For it to work here reliably, Vivo would have to make a new version to support the US market.
Every carrier, from AT&T to Verizon, cares about the variety of phones it sells.
"We don't want to just flood the market with a ton of devices," Sprint's Director of Product Procurement, John Tudhope, told CNET over the phone. We need to make sure we're doing smart things around inventory control and cost."
That means wireless networks decide in advance how many phones it wants to sell at each pricing level and gives phonemakers a chance to bid on getting their devices into the carrier's portfolio.
The networks might go with one over another if it's got an innovative or interesting feature (the wild card), or if they've got a good track record with the partner. In the US, Tudhope says, Apple, Samsung and LG phones rise to the top because they're household names.
"Other OEMs [the phonemakers] are like, 'I don't care how little you sell of this, just give me a chance,'" Tudhope said. "It's literally different every time."
Certification is the long, involved testing process that's designed to make sure the phone will play nice with the network. It's one every phone has to go through before getting T-Mobile, Sprint, AT&T or Verizon's seal of approval.
Remember, certification is your guarantee that the phone you buy works with every carrier band, including roaming bands. It also ensures that your phone connects to the network quickly -- and stays connected -- so you're not getting a lot of dropped calls or slow upload and download speeds.
There's a long list of lab tests that a phone has to pass, it takes a long time, and certification is expensive. Some brands opt to bypass carrier certification and go for a lighter touch approach -- standard FCC certification and limited carrier tests -- which costs far less and places the onus of quality control and support on the devicemaker.
If you do want more choices than your favorite network allows, buying a phone on the open market -- that is, directly from the manufacturer or from a retailer -- is the way to branch out.
Use your judgment. Buying a Pixel from the Google Store or phones from Motorola's and OnePlus' sites is a safe bet. (Note that Verizon also sells a version of the Pixel 2 and Pixel 2 XL certified for its network.) Getting that refurb from Phonez4Cheap123 on eBay, less so.
You can also go through reputable online stores like Amazon, Best Buy, NewEgg, B&H and so on. Sites like Sony Mobile link to its authorized retailer partners when you're ready to buy. Amazon's deals for Amazon Prime members usually sheds up to $50 off the asking price. Target and Walmart often sell entry-level and midrange models, too.
Just don't expect the same level of customer service that you'd get from a carrier-blessed phone.
How to choose a phone in 2018: So you think you're ready for a new phone? Read this first.
The best phones on this market: There are tons of phones out there. These are the best ones.