Maybe a couple of fighters have stinky feet and rather than singling them out and embarrassing them they just instituted it for everyone.
Any Europeans in this thread? Is it still a big deal that an Adult male shouldn't wear shorts if he is old enough for pants or is that tradition a bit antiquated. If it's still in effect, expanding into the Euro market might be valid reason for requiring pants.
Nah, it's totally ok to wear shorts in Europe: