I’m not so sure about the self checkout. I would rather say this was engineered by stores. From what I remember stores have on purpose replaced cashiers with self checkout machines, leaving only one or two. This resulted with long queues and forced people to self-checkout.

I still hate self-checkout machines and always try to avoid them. But queues now are unbearable and of course, now that machines are there, staff is expected to do more than just checkout. So they often leave their spot and you can only use the machine.

Labor is replaced on purpose, with a strict plan. Also, everything you do in store is precisely managed (single route from entrance to exit without a way to skip any section, bread at the far end of the store, product layout on specific shelves and near checkout)

I don't believe this was a result of organic demand from customers.