I think the real question is "does the existence of unicorns provide an incentive to the average founder?", and I'd say that question's a lot less definitive.

Sure, some founders have gotten filthy stinkin' rich off their startups, but those are lottery-ticket odds. Most founders seem to be aiming for either a self-sustaining small business or an acqui-hire, both of which are middle- to upper-middle-class career paths, but neither are by and large own-your-own-helicopter-class career paths.