Embarrassed for anyone else to see the junk they are buying.
Also, there is something psychological about the line moving quicker in a self-checkout, because there is only one line for multiple registers. I've been kinda getting annoyed through, because some stores people role up with a full fucking cart instead of like 10-15 items.
Target isn't that way, which is what I was thinking of when I said that. But also, I've never seen a grocery store employee kick anyone out of the self checkout line, even when they have way more than 10-15 items.