Well the reason you don't see more features in OBJ export is that OBJ is a pretty deadend format now. Apps support it for legacy reasons but all the cool new features are being added to COLLADA and FBX. COLLADA for example is open source, supports animation, bones, weight maps etc and you can extend it to export whatever you like. In comparison OBJ is very limited so devs don't bother much beyond basic mesh export/import.