It's possible that this perception of undifferentiated gossiping masses may be affected by bias in what the named characters listen to. The male population of Hogwarts might well seem like an undifferentiated Quidditch-loving mass if it weren't for Harry's tendency to fling Quieting Charms around when he wants to get out of conversation. (And, as a more literary reason, the girls' gossip is often plot-relevant whereas Quidditch jabberings wouldn't be.)