I don't understand why so many websites insist on using valid email/phone and password at the same time. Just implement login via email/sms and that's about it

I don't understand why so many websites insist on using valid email/phone and password at the same time. Just implement login via email/sms and that's about it. Now when it comes to this "phone" authentication, I'm not sure that I like this idea. I have good control over my phone number. I have good control over my domain and email (that's not true for most users, but they have the option). But making all my digital life depending on Apple or Google: that I don't like.