Pretty much everyone has, but that’s not the problem here. What if you don’t really want to give them a unique identification number like that? What if you don’t want them them to know you that well? What if you’re not even planning to use your real name at all.
Yeah but who doesn’t have at least a cell phone these days (unless you’re making many accounts)? They’re useful for 2 factor authentication too.
Pretty much everyone has, but that’s not the problem here. What if you don’t really want to give them a unique identification number like that? What if you don’t want them them to know you that well? What if you’re not even planning to use your real name at all.