Because it seems to me that whenever I go to the trouble of washing it or having it washed a bird promptly poops on it.
Maybe there's something about the newly washed shine that attracts birds? Or maybe it's just the Universe having a giggle, I don't know.
I just know that a) birds seem to always poop on my car just after I wash it and b) if a bird ever poops on my windshield, it is invariably right smack dab in my area of vision. Like, right at eye level.
*shakes fist at little birdies who poop on cars*