Most likely they want new accounts with something like a phone number attached.

To my knowledge companies can’t force legacy accounts into providing that.

But they can nuke those accounts for ba reasons, with the expectation most users will make a new account.

Even if it’s not the phone number, it could be something in terms and services about selling data or advertising.

Like, it doesn’t have to be incompetence, loads of companies use incompetence as plausible deniability for something else.