IDK, it's not that they are bad, it's just that there are better options out there. I think the main thing is that you have to play something super-ergonomic before you realize why anyone would want to play an ergonomic guitar over a classic shape, and even then, most people probably hate the ergonomic shape until they are able to play something slightly more ergonomic than what they are used to playing. Like, you might love pizza, and hate seafood, but then one day you try a pizza in Baltimore, MD, and it has seafood on it, and then you think, "gee, that wasn't so bad," and the next thing you know, you want that pizza with the seafood on it, then, after maybe a couple of years, you are just eating seafood. Another loosely related thing is the violin. Violin playing and building really peaked in the rate of its improvement with Stradivarius. Since then, the design has improved significantly, but progress has been much slower. People still prize violins from that era above all else, though. But, you know what? If you look inside a Stradivarius violin, you'll see modernized modifications of some sort, guaranteed. So, the pace of guitar design and playing improving peaked in the early 60's and then again with EVH. So, the LP, T, and S style guitars are, by far, most common, but usually with some modern improvements, and then the Superstrat follows not far behind. If someone comes along with a Gittler or some other wild-looking thing, and manages to reach widespread mass appeal through guitar playing, then I'm sure that'll all change again.