That's a pretty good comeback if you're in the mood to have a discussion.

Let's say you're NOT in a mood for a discussion with a stranger and they ask "Why are you wearing a kilt"... a good answer is "why are you wearing pants?" you'll either get a puzzled look (and a chance to walk away) or a snappy comeback like "b/c I need to cover myself" (to which you simply reply... "so do I")

If you'd like the "funny" answer, then say "b/c I need a bit more room 'down there' than most men".