I actually experienced it in other games on a scale that one doesn't even dare to imagine, so it is fairly easier to believe that it is done than it is to believe that it isn't done
There were users with 120+ accounts (4 of them officially accused, weirdly from 4 different countries - I can only imagine how many more, the small fish, got away)
I do agree though, that after a certain (extended) period of time, training players for either personal glory or a NT becomes realistically more fun than actually fiddling around with the rest of the game mechanics. But that period is of 5-6+ years of already playing the game and checking most objectives off the list. I am doing it in other games as well, but would have never done it to begin with (or for the first 4-5 years of game play)
I am kind of impressed with how under and over the rug this topic is though