But thats not how things are done in games - the textures are generated, then cached as traditional textures for use on the video card. So you don't have any quality benifit from procedural techniques, and in most cases loose quality because an artist cannot simply grab the brush and paint some pixels.
If procedural textures are going to become a mainstream in game graphics, it's not going to work the way it does now. These approaches are mathmatical in nature, and require a special kind of thought process which is quite different from how artists trained in traditional painting think. Additionally, we have more than enough storage on modern hardware, and more on the way, so it's not like we'e hurting for space or anything. If these textures were being generated on the fly, per frame, then they might offer some advantages, but thats not really a good use of the processing power right now.