The positions
You can watch most VR porn videos from a traditional third-party perspective, but the big sell of the idea is that you can also watch them from the point of view of of the person (typically a man, though you can find female-centric VR porn titles if you dig) being pleasured. This sounds cool in the abstract, but in reality it causes problems.
For this kind of video to feel realistic, you need to put yourself in the same position as the subject, whether they're lying down, sitting in a chair, or whatever else. Depending on where you are, this can be difficult, particularly if the physics of your chair, couch, or bed make the subject's position tiresome to maintain.
But even if you find the perfect viewing angle, maintaining that illusion requires changing position whenever the subject does, which is certainly more finagling than most people want to do while masturbating.
