Keep in mind maybe in the aas world it's different, but rarely does the Dea for example, go straight to the source...they need as much evidence as possible, so they will snatch up users. If you think about it, who has more to lose the top dog, or the user? Maybe if speaking of say a rock bottom drug user, not much...but the Doctor that has a secret drug habit, will sell out his own mother if that's what it takes, and the feds know this. The weakest link most times is the user. They threaten them with football numbers, and they end up agreeing to do controlled purchases, then boom you the dealer...the life you once knew, is over.
I've lost a lot of friends to prison, because of rats throughout my lifetime, and it was always a user that sold them out. I have friends doing 40 plus years in the feds (85% must be served, no federal parole). Aas though is different, in the sense that most sources aren't working for a huge organization, that is brining in 100s of millions in gear, so going after the source directly is in a sense like going after that Doctor that just likes getting high on the weekends, and got caught up.
Honestly some or the nicest people I've met, were sources..not so much when I've met dealers!