They don't want Nadal to get more points and eventually capture what is rightfully his (the #1 ranking). They know Federer can't beat Nadal on clay so they're trying to give him the best possible shot on surfaces like hard court (which Nadal still would own him on, see Dubai final for reference). Any sane-minded individual already knows that Nadal is the best in the world. This is an attempt by the ATP to maintain Federer as the supposed Tiger Woods of tennis. He ain't no Tiger, though.