Though true, that isn't really relevant, as those aren't the players this is geared towards. (And luckily, there's not really very many of those anyway, despite how anecdotes about them make it seem more common than it is.)
Yes, they were supposed to. But how often does anyone get a chance to run any of those dungeons legitimately, following all the mechanics and really maximizing their abilities? You're almost always going to get stuck with a bunch of endgame players who are just farming it or racing through their roulettes. All the dungeons that people are supposed to be learning from have been turned into mindless zergfests instead. No matter how much someone wants to learn their job, they aren't going to learn much in that sort of run, and getting anything else is too rare to count on.
About the only way to get a good dungeon run you can really learn from is to get a full group who are all on-level for the dungeon, in mostly white gear, and who are all trying to run it perfectly and as-designed. That's certainly not going to happen through DF, and even if you're lucky enough to have a good group of on-level friends and can manage this, you're only going to get one chance to run any given dungeon on-level and then maybe one more while you're only slightly over-leveled for it.
Back when the game had just come out, and most players were new, it was a bit easier to actually practice group dynamics in dungeon runs, but that just doesn't seem to happen any more. I wish learning it there still worked, but unless someone has some feasible ideas about how to keep people from zerging through them, we need to come up with an alternative training ground. That's where Correl's suggestions come in. Sure, it wouldn't help players who don't care about it. (Those players likely wouldn't even use such a feature anyway.) But it would be good to provide players who want to get better at playing a chance to learn how.