I used to work at a major multi-billion dollar retailer. One of the biggest complaints from customers was waiting at the check out line, especially for small, quick orders. This is the future of grocery stores, like it or not. Employees are expensive and make mistakes, whereas machines are cheap, don't take breaks, and work pretty reliably once you set them up correctly.
machines implement stupid broken ux patterns which make shopping hell. on edit: evidently people would like their supermarket checkout experience to be as pleasing as the typical online shopping experience, thus a quick downvote.
Most stores I visited don't even have scales and just trust you to put in the correct items. Especially the ones where you get a handheld device to scan while you walk trough the store. I would guess that fraud levels are much lower here so the stores don't need to do that.