Your point is completely orthogonal to account takeover. You can require a phone number to create an account and not allow SMS to the number to takeover the account.
What happens when the owner of the number discontinues the phone service, loses the number and the same number is give to another customer who then tries to register for an account on the same platform? Phone providers may recycle numbers in as short a period as a few months.
Not really. Some security vs. accessibility/usability trade-offs need to be made.
Somebody stealing the contents of my bank deposit box? Okay, that would suck.
Somebody breaking into the shed and stealing that old broken Toyota diff lock actuator I *swear* I'm going to fix at some point and maybe a shovel? Please.
This is why I think there might be a security floor for critical applications, but it should be the user's choice if they really want full 2FA+ with smartphones, biometry, and social security number verification for their random account on once-a-month-visited social network for cats.