From a technical standpoint it's trivial to identify and block voip services. Phone verification isn't designed to stop spam, it's designed to make it prohibit

From a technical standpoint it's trivial to identify and block voip services. Phone verification isn't designed to stop spam, it's designed to make it prohibitively expensive to scale spamming, and it seems pretty good at that. If you want to get around phone verification in a quick one-off fashion, yes it's going to be really easy. But there's no way to automate that one-off end run at scale without a lot of money and/or a lot of people. That's the whole point.