Because they ban a substance nobody else bans for superficial reasons. The IOC is so corrupt and has such ridiculous policies. It's all embarrassing.
It's banned by WADA, not the IOC. I spent 5 years under random drug testing playing football, there's a million things that are banned, we were reminded of it everyday and had a seminar at the start and end of each season. Many of them are innocuous if they aren't being used maliciously, but there are people using these seemingly innocuous substances intentionally to gain an advantage or mask something else used to gain an advantage.
There is no way that these guys and the staff of the teams can be ignorant of it. Most embarrassing for them.