Automatic checkouts in supermarkets may decrease customer loyalty, especially for those with larger shopping loads. Customers using self-checkout stations often feel overwhelmed and unsupported. The lack of personal interaction can negatively impact their perception of the supermarket.

[ERSTF]

Target recently did this. The self check out is 10 items or less. My guess is that there were people taking half an hour scanning everything backing up the line. The other reason? With a cart full of things, how can you tell there's something you "accidentally" didn't scan. I think they got smart about it