I've heard of every reason in the book:
*don't want to have to dump their tank as much
*don't want to have to clean the bathroom as often
*I figure some folks just enjoy the walk
*the best excuse I've heard...the gentleman of the house allows his lady to have the onboard bathroom all to herself...awww isn't that sweet!
When we park at our favorite state park in Ohio near the hometown...all they have is power so you bet we take a walk as often as possible and us their shower too. Having to move to fill and dump during a month long stay is way beyond obnoxious!