I think it's probably because to take that plunge and go all-out with a venture (which is how most tech startups work) you can't really have kids and a wife and

I think it's probably because to take that plunge and go all-out with a venture (which is how most tech startups work) you can't really have kids and a wife and a mortgage and the need for health insurance weighing you down and dividing your attention. Now that it's becoming more practical to bootstrap yourself into existence on the side - primarily because of cloud resources, but also just because it's getting easier in terms of support structure - I think we're going to see more older entrepreneurs. I mean, I'm 44 and I'm only now starting to get interested in startups. [I tell my wife similar things about physics when she gets despondent about not getting ahead in the field fast enough. There, I really think that the daily grind of academia, plus the terrible burden of having a professional reputation, is what makes it impossible for older folks to contribute the big stuff.]