The same reason that there's the "no alcoholic beverages" rule right above the "no pissing" rule. Once upon a time someone either did it in poor taste or compl

The same reason that there's the "no alcoholic beverages" rule right above the "no pissing" rule. Once upon a time someone either did it in poor taste or complained in poor taste and now it's against the rules and there's yet another entry on the big sign by the boat launch saying so. So everyone keeps doing it but they have to hide it for plausible deniability.