Hair is a very difficult thing to make in video games, often it leads to clipping or just plain looking really weird in general because longer hair have different physics. There are also stories of game companies actually hireing another company to just do hair (I think it was the Alice Madness Returns game?) because they wanted the hair a certain way, comparatively there is the Tombraider game recently released where it actually takes a stupidly powerful graphics card and processor to do the new physics hair (which is optional but was totally created to show off the tech either way)
So, having a character have short hair makes it easier to avoid weird issues or having to designate a team to just hair physics. In a massive rpg where there are lots of characters, all having to program such complicated hair would be such a drain on things that could be more importantly worked on.
We've only just gotten to the level of tech where clothing moves in a very flowy way, having hair react constently to head movements could end up making it look really other worldly (IE the Alice Madness Returns hair always blowing around into her face like it was made of spiders webbing rather then actual hair to me, but worked in the strange world) generally in a bad way.
This is also a dark fantasy game, you can justify the short hair in a number of ways. Such as-
-Long hair is easy to grab in a fight.
-Long hair takes more treatment
-Long hair is contently in the way and getting caught on things
-Long hair and helmets are the worse thing ever
And as a person with stupidly long hair, I can't see a warrior with long locks without going "That must be so heavy when wet..." or wondering how when a person even just brushes their hand through it, it isn't getting tangled in about twenty spots even if you've combed it recently.
But generally I just don't think the tech is there to make it look properly. So the designers have to keep that in mind unless they're perfectly fine with clipping everywhere like what most JRPGs do when their characters hairs reach their feet (different mood and different worlds between comparing the two genres I know but it still gives a sense to what sort of character designs each side goes for. Style over Logic or whatever word would go there)