The purpose of science related PhDs has always seemed to be a means to an end that wasn't financially available anywhere else. Academically, there are a lot of pursuits that you simply can not pursue outside of that setting. The science PhD is ultimately the direction you want your career to take, but you know it can't realistically take that path without some luck. And of course, the safety of academia is intoxicating on all levels. Why dive head first into research that requires funding and years of preparation when you can basically do the same thing at school without any repercussions? The PhD is a safety net for abstract thought that has little to do with the real world.
It may seem like a crazy comparison, but the sort of struggles scientists go through with their research is not entirely unlike what an artists goes through. No one really wants to acknowledge your absurd existence, and there's not really anyone to talk to when you do get on the outside. So no, success, be it financially or scientifically does not require higher education. But socially and emotionally, you can't underestimate the importance of things like a PhD.