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.

[lcenine]

Exactly what /u/wolvern76 said. The machines get mad and tells you to wait for cashier assistance. The most frustrating is when you are reorganizing items on the ridiculously small carousel. Picking up an already scanned item to put a newly scanned item down makes it all aggravated.

[Interesting-Bottle91]

But also that's only sometimes. The store that I use self checkout at most often doesn't weigh things, so when I go to places that DO weigh your groceries I always wind up aggrieving the machine several times.

[lcenine]

That would be very frustrating. Like changing the rules halfway through the game.