Men can aim, it's just that the trajectory of the piss isn't always too predictable. Sometimes the stream just goes in a different direction than you had expected. Orifices aren't that predictable.
Have you ever tried pouring water from a glass, only to find that the water runs down the glass instead of going straight down? That might happen towards the end of a peeing-session, when pressure is sinking.
Oh, and the infamous "split stream". That one's always delightful.
I always clean up if I make a mess though. Anything else would be gross.
You know, sometimes I wonder why I don't just sit.
[sub]Men are supposed to stand, damnit! That's just what we do. We are gifted with the ability to stand, and we'll be damned if we don't use it to its fullest.[/sub]