Really? That seems odd, where are you looking? Through your Carrier or just for unlocked devices? Depending on who you're with, usually you can just grab an unlocked device and your Carrier to register the device. I've only ever used Google Fi and AT&T though I'm not sure about the others.

Searching duckduckgo for 'Unlocked {device}' returns a lot of results on the shopping tab for phones on Amazon and eBay like the pixel 8/9 plus plenty of other "recent" android devices. Walmart and Bestbuy seem to still have dedicated sections for unlocked phones as well.

They are different kinds of unlocked! Unlocked generally just means "can be used with any carrier". For example this Samsung S22 I am on is "unlocked".

But Samsung hasn't allowed unlocking the bootloader on their phones for many years. And they are far far from the only ones in that state.

You basically have to research each specific phone far ahead of time. And beware! Because there's, for example, lots of guides telling you how to unlock my S22 phone. But as of ~2023 Samsung now blocks all those previous exploits that the unlocked software used to use.

It's a mess and a half.