When you're nabbed by the state at a young age and raised to do one thing, wherein there are zero prospects beyond the role given to you, and the real possibility of retribution - you do as you're told in all manner of things. It's not just 'doping' , it's basically a submission to the system on most levels.
'Doping' would have been one of the many things those people would have been effectively required to do as a function of their responsibilities, aware of it or not.
In America, you could argue children are coopted by their parents, but by the time of adulthood, it's entirely reasonable for people to break free of that. Even most children have the ability to rebel on some level. Tiger Woods seemed to love Golf long after he was good. Michael Jackson obviously didn't fare so well ...
Lance Armstrong made a choice, but any athlete in such an authoritarian system is not making many choices.