you are women, how would you know what its like to be peeing standing up... its not the easiest thing in the world, and if your drunk or fucked up on something.. or just not paying attention... your going to miss.
Because guys like to mark their territory with their urine. Its genetics, its in our blood to do it. So when we piss on the seat/ground etc, all we're saying is this is our territory. Good enough explanation?