Maybe it stems from a concern that the urinal will fill up and spill over onto your shoes?

Dunno about that, but I can tell you that Mrs. Walker at Hudson Elementary School did not like it when John Contreras and I did the overflowing urinal thing for fun... My ass hurt from the swats we got later... And that damn dude, that was the second time I got a swat hanging out with him, he was a bad influence. Of course playing hooky in first grade was kinda dumb...