What’s up with that?

In an attempt to help them pursue their higher education goals without acquiring massive amounts of debt, my husband and I share our home with our two college student children, ages 22 and 24. Between us, we have seven full or part time jobs and four vehicles. (Five if you count the horse trailor.) The kids bounce back and forth between their jobs, classes and home like those little steel marbles in a pinball machine. The four of us rarely eat together. We don’t leave or arrive at home at the same time on any given weekday and everyone rises and retires at different hours of the day and night. On Sundays, we attend church services at two different hours.
So would someone please explain to me why it is, without fail, no fewer than two people need the bathroom at the same time!?
My youngest has been potty trained for 20 years now and we have never lived in a house that had more than one bathroom, so wouldn’t you think we would have mastered the technique of sharing it by now?
Here’s a typical scenario; it’s mid to late evening on an average weekday. The bathroom sits silently, just off the southeast corner of the kitchen. It has been unoccupied for the past eight hours. One person is working on the computer; another is at the kitchen table working a Sudoku puzzle, a third is in the living room watching TV; a fourth (me) is washing dishes. At some mysterious cue, that only contentious people can hear, one set of footsteps crosses the kitchen toward the bathroom door, someone else looks up from whatever they were doing and shouts, “WAIT! Can I use it before you get in there? I really need to go.”
The first party retorts, “I was here first, you’ll just have to wait your turn.” This is followed by the door slamming.
The one who is left waiting says, “For crying out loud, you always take forever!” and then begins to pace angrily.
“I was just getting ready to go in there,” says the one looking up from his puzzle. He abandons the Sudoku and sits with arms and legs crossed, scowling at the closed door. After a few minutes, he looks at the clock and begins to mutter curses and threats.
I stare into the wall in front of the sink and try not let anyone hear the water running as I continue my dishwashing.
Not soon enough, the sounds of flushing and hand washing filters through the closed door. The waiting person stomps to the closed door, pounds on it and shouts, “Hurry up! I’m in pain here! How long does it take one person to dry her hands?”
Much to everyone’s relief, the door finally opens and the party of the first part strolls out nonchalantly, pretending to be unaware of the weeping and gnashing of teeth she has caused by her visit to the bathroom.
This is followed by, “It’s about time!”
The third one leaps up and shouts, “WAIT! Can I use it before you get in there?”
This is followed by the door slamming again.
Maybe we should just let them go into debt….