Really it comes from a lack of things to do. There's only so may times a person can play through XML2 or MUA, no matter how many mods there are, and pretty much all the major characters are represented with many custom skins to choose from as well. It's a strange place where we need a major overhaul mod (I.E. 100% custom levels or things like that) but we don't have the tools to do such.
I've toyed with the idea of seeing whether the custom character models that work on the Wii will work on original Xbox or 360, but in the end I've probably played through MUA 15 times, and my motivation is pretty low.
Still, I wish everyone the best -- just being a realist I guess