Cynical people don't found unicorn startups, don't win marathons and seldom the Nobel prize. On the other hand, not being cynical increases your chance to achieve such goals by 0.00001%, while your chance to end up a broke hobo, a beat down athlete or a 50 y/o teaching assistant waiting for tenure shoot up exponentially.

All in all, cynicism sounds (to a cynic) like a pretty good adaptation strategy to the real world.