Tour de L'Idiots

The thing I don't get about doping, which I'm thinking of since the Tour de France winner now tested positive on both tests, and hence will probably have his win annulled, is what's in it for the athletes? Is the financial and social bonus really big enough for winning that it's worth doing it in a way which robs your own ego of the win? I thought athletes had enormous egos, in addition to supersized lungs and hearts. In the meantime, they're screwing it up for everybody. Fuckers.