[mikestew]

so you win X race/competition once and then what?

So now you're on a Wheaties box and making millions in endorsements, that's what.

Even if it shortens their life, many athletes would take a drug that guarantees athletic success: https://en.wikipedia.org/wiki/Goldman%27s_dilemma The results have been disputed, but the take-away for me is that athletes have a variety of motivations, and the perceived rewards might be very different than what you might find rewarding.