SMS isn't about protecting your account from hackers, it's about protecting the service from bots. You'll notice if you have a VOIP account that the number can't be used to set up something like a GMail account, it requires an honest to god phone number, something you presumably paid money for. If you try to sign up a hundred accounts using one number you can be assured that it will cut you off very quickly. This is true of all major services.
This is also why they won't let you set up a good 2 factor authentication system (like a Yubikey) they'll force you to first set up a SMS 2 factor. It's very important to remember to delete that SMS second factor after setting up your good second factor or social engineers will use it to steal your account.
This is also why they won't let you set up a good 2 factor authentication system (like a Yubikey) they'll force you to first set up a SMS 2 factor. It's very important to remember to delete that SMS second factor after setting up your good second factor or social engineers will use it to steal your account.