The trouble is - the science of the cheats moves forward all the time so we don't identify them so readily at the time. Tomorrow, some new test might be found that shows some hero or another took something to gain muscle or power or stamina advantages. We just dont knowAnyone that does take something now will be caught. The vast majority are now just well built, eat at least 5-6 thousand calories every day and spend most of their working week in the gym.
Must say if they completely relaxed the rules it'd make it dangerous but very entertaining. I know I'd pay to watch that hedgehog mascot at the other end of the stadium get taken out by a shotput and javelins end up in the carpark.