Why?

I know this is a pretty shallow follow up to my previous post, but I had to ask. I'm not seriously upset about this or anything, but can anybody tell me why automatic windows on cars will roll your window down but not back up? Jason Miller told me it's because you can't get your finger/head/various extremity caught in the window rolling it down but you can rolling it up. But ya know what, I don't buy that. You're telling me they can't put a sensor on it or something? My garage door could do that when I was in 4th grade. Surely by now they'd have figured that out. Sounds like something they'd complain about on Seinfeld.