Well because its true. Hard work for an athlete is even more important than hard work for getting rich. Luck and being in the right place, knowing the right people, right things, etc are all far more important these days for wealth than how many hours you put in at the office.

With athletics there are bunch of pre-reqs, and a lot of luck but for most physical sports your going to have to work as hard as you possibly can for years. The genetics and working hard makes you a competitor, then you have to find an edge to actually win.