it takes the decision off the back of the cashier, and even the manager.

We can accuse the cashier and the manager of being "incompetent" or "not empowered", but we cannot accuse them of being racist, sexist, homophobic, or any other kind of discriminator. "The computer won't let me do it" is pretty non-discriminatory. "I don't know how to make it do that" may reflect poorly on the training, but not the person who is looking at the customer.