Because as you said yourself it's a net gain for the economy, a good investment. By now he'll have paid back many times more in taxes than he took in those early days. Hell, one of the arguments in favor of having some kind of social welfare safety net is that it encourages people to be entrepreneurs instead of just staying with the safest job they can find.

I would sure as hell rather subsidize a startup entrepreneur than the people who would, statistically speaking, otherwise be occupying that Section 8 housing unit. Does that make me a bad person? So be it.