Taking a risk for a big payoff is one thing, but many people (without any other kind of safety net - e.g. a wealthy family) will not want to experience the flip side of risk i.e. failure, given that it could entail losing their job or livelihood. Keeping what you have, which is tangible, is worth more than some intangible reward that may or may not come your way.

I'm all for taking a risk, providing I don't have to suffer too much if it all goes wrong!