Are you sure it's not because customers are choosing the self checkouts more and they need to meet demand?

I saw in my grocery store how, even when they had all available staff working the registers, the longest line would tend to the self checkout. This past summer they doubled the self-serve area.

The interesting thing is even though all full-service registers were in use, the deepest queue in any of them was two waiters. That means shoppers' perception of too long a line has shifted because of self-serve. They were choosing self-serve based on the belief it would be quicker, even if it means standing in the longest line. And that was mostly born out, mostly because the choice also depended on how many items were being purchased. People buying many things went to full-serve, which makes waiting in the longer, which drives people with hand baskets or half-full buggies to the self-serve.

The upshot being stores are installing more self-service checkouts because customers want them. It's not like adding those self-service lanes comes at no cost to the business. In the above grocery store, they had to remove part of the floor they previously used to display products. If they didn't think it was necessary they wouldn't have done away with that selling space.

I mean, that was what one of the managers told me, and I can see that they don't have a whole lot of staff at times that it would make sense to have more staff.

Also, the lanes they added were in addition to the ~12 basket self checkouts. The new lanes are setup for people pushing carts.

This to me means they're also selling more pre-packaged items with scanable bar codes rather than they are items like fresh produce which requires a lookup and weight check at checkout.

Everybody, everywhere is moving to self-checkouts. It's about entirely eliminating staff, not that staff is now a few percentages more expensive in some places.