T20, it's very simple really.
If you start when you are weak and small...say 150 lbs than you will learn to rely on gear for gains. If you never made any real progress as a natural,,,something is wrong(diet, training, rest).
Some people don't take the time to figure out what's wrong with their diet or training...their solution is drugs. When they come off the drugs...all those mistakes that held them back as naturals...will hold them back as juicers. They never bothered to correct those mistakes and they are repeating them.
Typically, these are the guys who lose everything when coming off. They owe most if not all their success to steroids. Sure they will gain great off there first couple of cycles...but then the gains slow down. They are using grams of gear, yet they look like they've just started training.