Hey, you know all those super 'secure' instant messengers, that use all kinds of super powerful encryption and stuff? Signal, Telegram, etc?
They'll all linked to your phone number. So all the Regime need do is request a new device or password reset, and since they own the telcos, they can get into your account.
Real secure. Allow the option of userid/password authentication rather than just a phone number you say? You wish. Signal and Telegram don't want to allow that. For Reasons.