Yeah, but even them you’d need to be careful in choosing the model, because so many manufacturers make it either impossible or very hard to unlock the bootloader!!

It is understandable that the answer is “because they can”. But another jarring thing is how common locked bootloaders are. You can make pretty much any random laptop privacy-respecting by installing Linux, but there is a good chance your random given phone cannot have things like Lineage?! Or they can but it is so complicated that might as well not count, like Xiaomi…

Writing the directions down on a paper is still more convenient than taking out and unlocking ypur phone if a) you’re on a bike; b) if it is cold out and you don’t want to take off your gloves.