Pacer2 uses the argument there's cheating in all sports, and the cheaters get caught, same goes for trainers. It's either being totally naive or stupid because as you say, not all illegal substances show up on tests.
Let’s wind the clock back 50+ years.
The East German swimmers on steroids in the Olympics.
The tragedy horses in the sakes that were built like linebackers.
Lance Armstrong getting caught.
In each case this took time to be caught and dealt with.