My guesses:

• Intoxication: They're drunk or high enough that they're not neurologically capable of aiming; the fact that they managed to get it out of their pants at all is astonishing.
• Narcissism: They're very important assistant sales managers, talking on their phone through the whole transaction, and aren't paying attention to what they're peeing on; just as they don't remove their dirty dishes from the office meeting rooms after a lunch meeting. Aren't the help supposed to do that?
• Helplessness and/or disgust: The toilet was already filthy when they came in, and they didn't think they were making it any worse.
• Peevishness: They got yelled at by a scary janitor once for sticking gum under desks.