I think this has been picked up elsewhere, possibly by the BBC. Unfortunately, I can't remember where I heard or read it, but I think it was on the Today programme on Radio 4 in an item about drug taking in sport. It was reported that it was rife in lower levels of union, not necessarily for performance enhancing reasons but for body image reasons. Apparently, players at that level want to be seen to have the necessary thick neck and bulky shoulders, even if they're not playing too often. There didn't appear to be any follow up though, and the whole issue just disappeared after that.
I think that's true at all sports. A bit more so in RU and RL due to the nature of the sport.