Heck no, I don't care about keeping my legs dry, and they wouldn't be dry in a wetsuit anyway. The object, at least for the crew, is to protect your legs from cuts and bruises.
If I were sailing in cold weather/water, I would wear a full wetsuit, but we don't get much of either down here. So bottoms-only would be perfect. As a bonus, if I were trying to lose weight in my lower half, I could wear them to bed.