Most of that was a problem with the glitches and banning systems. People are always going to cheat their way to get to the top. People AFKed for cR in Reach. I still see people doing glitches and boosting in Spops and MM.
What I want to know is who decided it was right to have a time-based progression system and wrong to have a skill-based progression system? Who sat there and decided unlocking armor and loadouts would keep people playing longer than achieving ranks in all the playlists?
All questions that forever go unanswered.
Cheating is much more prominent when there is the carrot of a rank though. And then you get kids whinging that the developer is not doing enough to combat cheaters.
Bungie had to employee people to solely develop, test and manage the ban hammer. That resource could be better used elsewhere.