What is difficult? To animate it? To live with it? To go to war with it? Do you see what the gymnastic girls in the Olympics do with their hair? It's pulled back in a tight bun or small pony, slathered with product (glitter optional!), and tamed with barrettes. Not a single strand goes awry because it can't during competition.
As someone else who also has long hair, if I were to join the military the very first thing I would do is chop it all off. There is no way in hell I would bother dealing with washing it, pulling it back, using product to manage flyaways, and all of that garbage when my male counterparts just do swish-swish with a tiny amount of shampoo and are done. I've had short hair periods in my life as well. It is considerably easier to live with. And yes, I do know that there are active servicewomen who do have long hair. If they can live with it good for them, it just wouldn't be my choice. But do notice that there are military regulations regarding the length and style of hair. You won't see any of those women going into combat with the hair featured in some of the DAO mods.
[edit]
I will say though that I really don't care what kind of hair players choose for their PC. The realism argument doesn't influence me in this case. It's a video game. While I personally think some of the styles are ridiculous, I certainly don't begrudge other players from using them. Whatever floats your boat.