There is always the threat of laying off staff instead of paying more, but only a relatively minor portion of management is enough of a maniac to actually go through with it. I worked at a McDonalds during a minimum wage hike (you can tell this was a long time ago), and while everybody said it would result in cut staff few went through with the threat. Sure you could find examples here and there, but at the end of the day they were already operating with the minimum amount of staff they could get away with. There was no slack in the system.
McDonalds corporate even realized this and started talking up fully automated restaurants. I think they even built a pilot store somewhere. They dust it off anytime people start talking about minimum wage hikes, even though it makes no sense economically even if we were to double the minimum wage overnight.
IMO, this is going to happen at some point anyways. It's only a matter of time.
In the short term, it's going to cost a LOT of money to develop, deploy, and work the bugs out. But in the long term, it means there's literally hundreds of thousands of workers they could replace. They will eventually see an RoI.
They will try to avoid it before the increase, and they will try harder after. That doesn't mean they can have a 100% unmanned mcdonalds if minimum wage somehow shot up to $30. And given that McDonald's main revenue isn't even on food, it's not even a good idea for that specific company to shut down locations over increased wages.*
That's clearly why they are investing more into those automated tellers. automation is the only way to reduce headcount but not affect throughput.
*Other chains might, though. I do wonder in this scenario if this would lead to small business rising up as large business find it untenable to hire entry level labor. I don't imagine so (they will pass the costs to the customer), but it's an interesting thought experiment.
Shenanigans. You've never worked in retail. Even if you come back claiming otherwise, I'm still going to accuse you of lying about it because you could only be more out of touch with reality if you claimed to be the ghost of Sam Walton himself.
"Necessary" staff does gets cut and the remaining employees are expected to pick up the slack. The alternative course is shaving hours off of the schedule for all employees. Sometimes they go both routes.
One way or another, the retailer will not bear that cost of increased wages. It gets suffered first by employees through reduced hours, then by customers in a degraded service experience.
You offer economic theory. I'm telling you from bitter experience what actually happens.