Why do road bikers wear tight shorts & mountain bikers wear baggy shorts? Are mountain bikers more modest?

Often, those baggy shorts are worn over a pair of tight shorts to protect them from snagging on thorns or tree branches. Over the years it has become something of a style thing for mountain bikers to wear baggy shorts. However, top cross country mountain bike racers almost always wear lycra shorts, just like road riders. None of this has anything to do with modesty