But I believe fundamentally most people don't want to make video calls. I use skype all the time, which has a video feature, but rarely use it. To me, video calling feels unnatural.
Furthermore, well it is practical in most situations to make a normal call, video calling only works in certain situations. For example, it won't work while you are walking, or otherwise occupied. As such, you have to make a conscious decision to this time use video calling, and not voice.
I don't think video calling will go much beyond a novelty feature.