Thing is, most of the lowest-level dungeons are stupidly easy even if you mess up on aggro, and lots of people know that and as a result don't really care about doing things properly. You can peel mobs off of the tank and not really take enough damage to trouble the healer, there's very little for healers to do at that level because they're synced down and lose most of their healing utility, DPS are reduced to two or three buttons, and tanks lose virtually their entire toolkit. It's not really a good experience for new people who actually want to learn how to play, but especially for people who are working on relics and might have had to do the same dungeon a couple of dozen times, they can probably do it with their eyes closed by that point and just want to get it over with.