HGH is naturally produced by the body and essential for one's well-being. It is not a steroid that causes exceptional strength or endurance. It helps to increase one's red blood cells and allows for better energy levels and to repair faster from injuries or traumas, which could be useful in professional sports. Their sport is their job and therefore they should have a body at full capacity. It is the same concept that actors have to go on extreme diets for their jobs.
HGH is not testosterone. While testosterone increases muscle size and strength, and has a large number of corresponding health problems associated with steroids, HGH is very different. While HGH doesn't have a huge effect on the size and strength of muscles, it does help the healing time of muscles, something that many athletes would benefit from.
If you want to watch finely engineered machines compete, then find your local robot wars club and watch those hunks of steel and plastic go to town on each other in a combat arena. If you want to watch humans using their finely trained, natural bodies compete, then go to a real sporting event. But please stop trying to engineer perfect athletes like they're some sort of programmable machines by injecting them with junk hormones.