One of the worst examples I've heard is that Overwatch 2 not only requires a phone number, but they actually check with your carrier if it's a prepaid number, and if it is, you're banned. Sorry poor people, Blizzard doesn't want scum like you playing their game.
Assuming someone's phone number never changes, or that they'll have access to their old and new numbers at the same time, is simply wrong and does not work.
I haven't been locked out of Google yet, somehow, but maybe it's just a matter of time.