Why Do Men Leave the Toilet Seat Up???

It's kind of like that feeling you get when you grab the milk in the fridge, expecting it to be heavy, but it's almost empty and you realize that too late as the jug hits the top of the refrigerator.
I don't know how many times this has happened to me but I know it's happened at least once because I can remember exactly how it felt. It was the middle of the night, dark and quiet. Quietly I felt my way into the bathroom, sleep in my eyes. Just a quick trip and I'll be back in bed. But no, I'm falling too far! There is nothing to stop me from falling. SPLASH! Ahhhh! Cold and wet and ooh! I'm IN the toilet!
If this has ever happened to you, you know what I'm talking about. So I pose the question: Why do men leave the toilet seat up? Since my early years I have been very particular about the toilet seat being down. In college I called my roommate's boyfriend back to the bathroom multiple times to put the seat down. When I married Chris we compromised by putting the seat and the lid down. That has worked great for us!
The other day my realtor sent a really nice, good-looking, clean-cut guy over to draw a floor plan of my house. As he headed upstairs he asked if he could use my bathroom. Sure, no problem.
Later that day I went into our hall bathroom where Tristan was playing with his Elmo table. He had been in multiple times that day to play with his toy. When I went in there, the toilet seat was up and I was really grossed out at the thought that my child could have gone over and played in the toilet water! Not to mention that kids have drowned in the toilet!
I was surprised that someone would come in my house, use the toilet, and not even put the seat down. I personally think it's good manners to put both the seat and the lid down. Am I alone on this issue?