Why several big-box stores have ditched their self-checkouts

They actually mention here (which other articles on this trend do not) that the real reason is nothing to do with customer dissatisfaction, or problems with the self-checkout machines, but rather that they saw an increase in theft.

Given the upsurge in scammers, porch pirates, etc. it does not seem implausible that they are seeing an increase in theft. It also seems like the sort of thing that would be low at first, but increase over time as more people realize that they can pretend to check out, but just "forget" an item or two and have virtually no risk (because even on the odd chance you do get caught, it's hard to prove it wasn't a mistake).