There are formal pants outfits for women. I have one - it is crepe with fly away pants and a lot of beading. It would really look silly as an informal or casual outfit.
Millennium-Transatlantic-9/01, 10/03, 11/05
Zenith-Special Caribbean 11/06
Back to back Millennium 28 days - Mediterranean 11/18/07, Transatlantic - 12/2/07