There is a severe lack of space if you're getting a lot of items and no good way to remove full bags without the thing yelling at you.

I used to scan and bag groceries in high school and the scanners on the self checkout slow me down significantly as well. Constantly flagging items as not bagged if I scan the next item too fast (even when bagged) or for not scanning items if I dare have something in my right hand while bagging with my left.

And yeah, I'll avoid the one line with a human where they're 4 deep with 50 items each wanting to pay with checks still.