I think the dropouts look at people like Steve Jobs and Bill Gates, etc, and want to say "Look! You can be rich and successful and influential without requiring some silly piece of paper and a goofy hat!". Therefore, I don't need it!

The PhDs and Computer Science grad students are likely to look up to people like Turing, Church, Von Neumann, John McCarthy (as he's been in the news) etc.., and be satisfied pondering The Secrets Of The Universe and be stimulated by working on extremely pure intellectual challenges.

To the dropout entrepreneur/hacker, the prospect of working in an office proving the lower bound of a routing problem over ad-hoc networks is about as bland as you can get.

To the computer science professor, post-doc, whatever, the prospect of working as some web-app developer or "java engineer" and hustling for customers is completely vapid.

I tend to slightly side with the academic CS types, since many people can teach themselves to be successful hackers independently, few college dropouts are architecting the next generation of internet protocols, contributing much to computational complexity theory, producing the next RSA cryptosystem or homomorphic encryption, or contributing to the algorithms to make higher-resolution images from MRI scans. On the other hand, if you drop out of college, this isn't probably the kind of stuff that would interest your blood pumping anyway.