Actually, I remain absolutely baffled that I don't see more mags out there. I always have felt that way. I always get 'ohhhs' and 'ahhhs' when I break out my mag, yet people don't use them. Why? They seem to have one of the best designs. You certainly would have trouble beating the support! And the quality is amazing. There are very few downsides to mags.
So why don't people use them?
Because, well, people are stupid, in many ways. They don't buy markers because they are the best and will be the best for years. They buy them cause they are 'new' and 'cool' and look great. From what I can see, the common style is to buy a new marker at least once a year. That said, why would you buy a mag? They last too damned long! The technology is nearly perfect in them. You don't need to tinker, you don't need to upgrade. In short, people with mags spend too much time, well, playing paintball, instead of tinkering on the sidelines. And that's what most people REALLY want to do.