Look back at the NFL in the 70's and early 80's. You had some serious steroid users in this time period. Because they have admitted to it. Public perception goes down and thus they aren't as accepted as they were 20-30 years ago. With the time frame you start to see a lot of thyroid problems and ligament injuries much more frequently than before.
Players start getting no drug clauses in their contracts and they have a lot to lose if caught.
Most players today will not ever admit to steroid use. They have too much to lose. So of course the players will say they are not using anymore and a lot of guys don't. This is mostly centered around lineman and trench dwellers. IMO the best place to play football anyway.