Of Windscreen washers and motorcycles...

...now if it had been a once off I would have thought nothing of it. But it's now happened to me a number of times. What is it with car drivers that makes them want to wash their windscreen when a motorcycle is behind them?
Do they think it's funny?
Do they get some kind of obscene pleasure from firing their misaligned jets of sudsy water at riders who have a hard enough time as it is trying to read drivers minds and anticipate every split second last minute lane change that brings threat to life and limb? Is it like listening to running water that makes the "bladder control" challenged go dashing for the nearest latrine? Is this phenomenon like the sudden urge to go?
If it is then, for God's sake cross your friggin legs and HOLD IT!
I just hope the light turns red on the next driver who showers me in sudsy water and bug splats so I get a chance to "thank" them in person.