It's the "matching the founder" thing, mostly. Mostly I didn't want to have the people with the "right" kind of hair wear it longer and everybody else have to cut theirs short, because that has unfortunate implications, at least to me. (And it's fanfic, so I don't get to pick the founder's hairstyle.) But I couldn't think of an alternative that had no possible unfortunate implications, because hair's so political.

(Also, I've gone through periods of combing shoulder-length hair only a few times a week, and just finger-smoothing it on the off-days, and it takes a lot longer than that to start to mat. Though, of course, it depends on texture.)