[ylere]

"most websites" has not been my experience at all. Sure, for the big ones like email that's and a lot of dev tooling that's the case. But there's a huge amount of services that requires SMS verification and once you loose access to that number you get locked out. A very common case is loosing ones phone (or having it stolen), at which point you have to log into your accounts again from another device but also don't have access to your SIM anymore.