You are conflating the alleged benefit of locking down devices to assure users don't break them [1], with websites and services getting the ability to remotely verify your software/hardware stack is "approved", and block you if it isn't.
It's not about what you want - it's about taking away your ability to choose. The "fun toys" that can be modified to your liking will get increasingly useless as they'll be blocked from large chunks of the web, especially after Google will start pushing WEI if sites want ad revenue, under the logic of preventing click-fraud.
[1] There are plenty of ways to limit unlocking to the technically-savvy, and making it tamper evident to the owner (e.g. a "bootloader unlocked" notification during boot), and many existing phones implement them, so any claims by phone or other device manufacturers that making devices impossible to unlock are outright lies.