The main deterrent for all crime is to actually catch them. As long as there is the certainty of being caught you can always change the penalty later to deter the criminal.
Athletes cheat for the money and social status that comes from success.
We're not generally talking about small amounts of money it's usually of similar if not greater size to that you would gain from robing a bank. If we consider the punishments in place for drug cheating in sport the current situation is the equivalent of trying to deter bank robbers by banning them from entering another bank for a few years and giving them what is little more than a traffic ticket. In virtually all cases the person who uses drugs to fraudulently attain money from sponsors etc gets to keep what they made before they were caught. This isn't really much of a deterrent. We don't have jail as an option for many reasons but the punishment has to be quite strict if we are going to deter people from stealing a million dollars.