It's not that VR isn't a big deal, but at this specific point in time, other things need the focus. I'd love to have hawken with vr. I got to test it out way back in the day when it was still possible to play it (from what I hear, if you have a dk1 you can still set it to 1280x720 and edit the settings and still get it to work actually, but you need the old oculus sdk to do it also.). There were problems (2d and 3d weren't working right at the same time, you could focus on one, but not the other), but was interesting to say the least. But, that said, I'd much rather have a hawken that has a vibrant community (as in lots of people playing) than a hawken with no one around but can do vr.
From a technical stand point, adding vr to hawken will be very hard. There is no native support for VR in unreal engine 3. (which is what hawken uses, and it's a very very long upgrade path to go from ue3 to ue4, as epic does not add an upgrade tool to do this for you.) Using UE4 would help a lot with hawken (better built in networking support, native vr support at the check of a box {if you made the ui right}, better framerates for same quality of graphics, etc) but would be a long path to go to get everything working (especially since last I heard, the networking in hawken is not the native networking for ue3).
So it's not "easy" at all to do this, and the benefit is very very low as opposed to other things. As stated, I'd love to see vr in hawken, but it doesn't make sense at the moment to put the resources on it. Sure, it may bring in a few people interested in vr, but new mechs and levels and game modes are an altogether better approach to getting new users than vr support would come close to.