I've never personally seen someone do that but I have heard stories of this happening before.

I have incontinence, so I either wear diapers (still going to pee and defecate regardless), or I have access to the bathroom in time. If I wear diapers, there is going to be odor contamination in the area. It is bad for others, and for me, and their business too, I assume. Depends on the length of the trip; I try to limit fluid intake to zero before I go outside.