Washing and detailing your car(s) alerts and summons the rain gods. It is the urban equivalent of a rain dance. In theory, it's not the rain which makes the car dirty. It's all the other crap in the air and road that sticks to the rain onto your truck. Yes, I do agree with you, it does indeed suck. Especially when you have just dressed your tires with something shining and then BAM!!! The wet road and rain dull them out. Just the pisser.