There's not really enough room for it. Most of them have one spot to put stuff, which as I recall, weighs it to make sure it adds up to what you're scanning. But there's not enough room for a full cart load to sit there, which messes up the whole point.

At least that's what I was told they're for. I've haven't seen one go off when there's extra weight there in a couple years now. Maybe they gave up on that part because people couldn't fit their stuff there.