I think most people in the supplement section are in the supplement section because they don't take steriods - if that makes any sense.
Most steriod users progress though their 'natural' phase, then they hit a plateu and realise by taking supplements they can still get bigger/stronger; so they do.
After you start taking steriods, I'd imagine you'd care a lot less about taking something like a 'natural test. booster', because your gear would be doing a lot, lot, more for you.