I suspect they didn't make more dynamic hair bin order to support the older PS3/360 systems but when they move to XB1 and Ps4 and stop supporting the older systems will be when we get there I think. After all we do have quite dynamic armour in DAI as I noticed Vivienne's armour blows in the wind as do a lot of the mage armours that I use on my inquisitor. I know the next ME is only going to be released on the newer systems so maybe all this will start to happen then. I won't hold my breath but I'd say there's a better chance things like this will happen then and for any DA or ME games that are released after this.
Actually I find it hard to believe because...well, I have played Dragon's Dogma on PS3. Almost sixty hairstyles, from long hair to short, to braided, to mohawke, to bald and everything in between. For both sexes. (I loved my viking with Obelix style pawn with red tresses
Sadly I made a new gameplay where I created basically Sten) the hair had some phisics, and where very good looking. (better than the DAI hair by a long shot). and even DA2 had a little movemant on hair.
and it was both old gen and limiting engine.
If there is a problem with the old gen, (speaking of hair) is mostly a texture problem. But I don't think it have to do with the dinamic hair. (not when everything else move)
Let's face it. BioWare have no idea how to do hair. And who make them have no taste. Are the only possible motivations. The more I look at others games, the more I see it. 
And yet, is not true even it. Because we have the old portrait, and they are great and tastefull. I would pay to use them in game! So why they didn't implemented those? I hightly doubt those where discarded because they thought people would have preferred all those shaved/balding styles!!! 