the people deciding this are the ones selling the devices
Well, I fear that loophole is quickly closing with little fanfare.
Pixels (barelly) running a binary-blob-heavy port of android is far from what is being discussed here. In fact, that is intended as a misdirection and you fell for it by bringing it in here.
The companies selling you the devices make 1/3 (appl) to 3/4 (alphabet) of their entire revenue on Advertising.
Owning the indentity layer ensures they get fully addressable ads, which is the difference of $12 per impression instead of $.0001 per thousand impressions. But nobody is ready for this conversation.