@Sep10trion
If I was to guess, I'd say that japan like many other nations in the area have a very insular culture. As a general rule, they don't enjoy things that are too different. I don't know much about the culture shift that caused the majority of school outfits to go towards the sailor style with the shorter skirt over the longer more traditional ones (ease of wear likely the biggest driver - a/c seems to be a rarity going by comics), but I'd guess that by using the older style the individuals could push against the general culture as much as they could without going too far (like getting a tattoo). It also is a great look as many would express. It might be another five to ten years before I see a comic book school girl with a shaved or buzz cut head as that pushes too far against what I see their current standard is. Shaving is seen as a punishment in comics.
Things are getting more expressive over there year by year, but it is very slow. The government in particular is extremely socially conservative. If they ever get rid of whaling, then I might admit to a shift in a positive direction.
I see the culture and sub-culture as a Venn diagram, where the sub-cultures might not overlap the primary culture completely, but the majority of it does.