Because the core reason is about control. They don't want users to have the option or freedom to install an OS of their choice because it could hurt their "precious" revenue

A lot of carrier phones come with carrier preinstalled apps. And it allows for sim locking, keeping you trapped with them or other carriers on the same network. Or at least that’s how it has been, back in the day, when sim-locking still was legal in the EU. Now, phones are the same, whether they come from your carrier or retail.

Their stated reason is to mitigate theft by preventing removal of software that binds the device to the network and account, and to protect their network by blocking paths to custom roms including potentially custom radio firmware.

The real reason is likely a blend of protecting leased devices for resale value, keeping people from removing "sponsored" apps or ones that make them money, and distrust of users ability to not get tricked into abject stupid choices.

You don't think they care that you're attempting to circumvent their data collection on you?

They care because some users don’t actually own their phones and the carrier wants to keep strings attached, or they want to impose artificial software restrictions like preventing or limiting hotspot data.

Even when none of those conditions apply, you still often must deal with the locked boot loader. It’s BS.

The concept was always bizarre to me. It's like getting a PC as part of your broadband contract. Speaking of, it would make more sense to get a phone as part of your broadband contract, my phone is 95% an internet device. That it happens to have a SIM card in it is a minor feature.

Ok. Now how do I unlock my samsung note 20 ultra that isn't carrier locked?

Especially US carriers. Elsewhere, it varies.

Expensive, but worth it.

This and bootkits.

Easy if you have money. If a new phone is a financial stretch, then in the short term it can be cheaper to get a nice phone for "free" with carrier lock in (which of course means it wasn't free at all). It probably ends up being more expensive in the long term, but your paycheck can cover it.

Unless you are Chinese user, which means you are double fucked.

To unlock your phone, you need to:

1. Level 5 Xiaomi Forum Level (Gonna take half a year if you only check in daily, if you post and replies, then its tiny bit faster.)
2. Make an appointment for the Unlocking Permission Test (random dates, xiaomi is also slowly/quietly limiting the number of test dates)
3. Pass the test (timed, broad range/difficult technical questions, akin to a 300 level college exam that you're not given any materials to study for)
4. If you pass, you're only allow to unlock 3 phones per year.

But hey, if you bought the phone outside of China (or simply not Chinese version), then you don't have to do any of those except wait for 68 hours. Fuck the Chinese users eh (Chinese version also has a lot more bloatwares, the apps that you download from xiaomi app store also more invasive (more permission) than google play versions).

I think it's 72h after linking your phone to your Xiaomi account, don't need their pc app abd tools work fine.

It's still one of the brands that are most open for custom roms since you'll retain your warranty unless you manage to do physical damage to the phone in the process.

Carrier locking != Bootloader unlocking

Welcome to capitalism...

For a long time VZW used separate tech. That required a different antenna/software. Hence special phones.

And still has some frequency bands not offered on international phones. But it is mostly about control.

I have a "budget" device from 2019. It runs Lineage OS and works fine.

Also you are the product

I am more than aware that not everyone can afford buying high priced phones right out. I should have clarified that in my post

When have you last used a mid range phone? It used to make a huge difference, but over the years, as phones matured, I feel it's shrunken down more and more. I used to always use flagships, but these days, I don't see what value they provide over 400-600€ phones in daily usage.

The best thing is actually to buy a used phone that was really good a couple years ago. I bought a used Oneplus 9 for $200 last year and it's still perfectly usable and way more powerful than I've ever needed a phone to be. Also older phones are more likely to be supported by third party android distributions.

While this is true, be aware there are drawbacks to 3rd party budget carriers.

The service includes caveats that your traffic lower priority then VZWs so if your on a busy node you may get throttled or temporarily kicked off