As Tim Burke points out in his excellent essay, "Should I Go To Graduate School?", grad school is "cotillion for eggheads". It's a tool for socializing individuals into the culture of academia.
Scholarship is a collective, social enterprise. Whether a professor is an expert in Elizabethan literature or particle physics, the one thing that professor will always be aware of is his or her reputation among academic peers. One who does not care about his or her scholarly reputation will not last long in academia.
Inventors are individualists. They may cooperate with others -- like Wilbur and Orville, or Edison and his minions, or von Braun and all of NASA -- but the collaboration is generally in the service of the individual vision. You cooperate with others because they can help you achieve your goals, not because you expect them to tell you what to do.
That's not to say that inventors don't care about others' opinions of their work -- they do -- but the dynamic is different. The inventor is likely to work away in his or her lab, alone or with a small group, until the invention is ready for unveiling. Only at that point is an inventor likely to seek public acclaim. Every inventor loves it when people say, "Oooh! Ahhh! Cool! Let me give you a million dollars!"
Of course, there are inventive people in academia, some of whom are very successful. But at some level it's like being a salmon swimming upstream. You may be successful in the end, but you'll be fighting your environment every step of the way.
Like most people who build robots, I've always been an inventor at heart. Academia was never a good fit. I'm a lot happier now that I have a job where I can spend most of my time thinking, "How can I get my next invention to work?" as opposed to, "What will the influential faculty in my field think about this?"
(Actually, I never spent too much time worrying about the latter question, but that was one of the many reasons I was ill-suited for academia...)
