My experience is the opposite, classic dungeon runs are plenty social, lots of talking and joking. I've made 4-5 battle.net friends just doing the occasional dungeons between lvl 30-60 in TBC classic. Maybe it's just my server has a good community but TBC Classic on Earthshaker EU has been an incredibly pleasant and social experience, much more so than it was ever was for me since I started retail in WotLK.
In fact I would say that yeah, the "after-school special" is alive and well on my server. It's very strange of you to say that these things NEVER happen and never did when it's patently false. Groups are talkative, mature, patient and it's very rare that people get upset. Of course, if you want a social experience, you are required to be social yourself. You won't make any friends if all you do is silently pilot your character.