Well, VR is a "new" field that many people are investing in after AI, and the most obvious application would be toward fulfilling dreams/pleasures previously impossible.
The problem is waiting for VR tools to become mainstream like an Xbox/Iphone, and many huge companies like Microsoft, Google and Valve are already putting in years to development.
I have yet to see a hentai title that I would "definitely" buy for my VR set, but then again I do have high expectations.
You had to start somewhere and build a fanbase if you want to get mass market content that is.