On the contrary, I'm perhaps a bit slower with the scanning, but I have the time to pack every item in the correct bag, without putting stuff on belts and without the heavy breathing of another person in my neck while their items are already playing a game of bowling against mine.

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.