This is so incorrect that it's hard to take seriously.
When revenues go down (for any reason), companies cut costs. Most employees are a cost. Why have 2 people when 1 will just have to work harder? A company rather cut and see what happens, when push comes to shove. Many company initiatives are also re-evaluated with a bottom-line mentality when revenues are down. That project that's 4 weeks overdue for a milestone? Time to cut it and everyone involved. When revenue is up, the opposite effect. "slack" is relative to market conditions. Job security along with it.
Small companies are often lean, but it's never surprising how much leaner they will run when money gets tight. Big companies can always pare down assets and associated headcount. These are just the things I see every time revenue is down, but far from an exhaustive list.
The problem is that is a failing paradigm these days and it's not uncommon to walk to up locations that say "closed, no staff".
If the 'no immigration' voices get there way expect to see a rapidly declining population here in the US and these businesses that are used to abusing labor start to freak out.
Beyond the low pay it is quite likely that the manager is an asshole and the reason he can't find workers is because for what he's offering there are loads of opportunities for jobs at better managed stores in the area. This is a person who was spoiled when the job market was tight and now can't adjust to a new reality where people have options and if you suck they won't choose you. If the business isn't profitable without effectively slave labor then it was poorly structured.
If there's a shortage of wheat, everyone expects the price of bread to go up. Everyone shrugs their shoulders and accepts it.
Shortage of oil? Gas prices go up. It sucks, but that's life.
Shortage of labor? NO, WE CAN'T INCREASE WAGES. UNACCEPTABLE. NOBODY WANTS TO WORK ANYMORE!
Your argument is completely wrong, yet you start by berating the other poster. Companies will always cut costs and try to whip their employees as much as they can, regardless of if they're making a profit or a loss. That is business.
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.
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.
If they have enough slack to reduce headcount they're going to do it anyway. Companies strive to hire enough people to get the job done and no more. They may not always get it right, but minor changes to expenses aren't going to affect headcount unless the company was already overstaffed and looking for an excuse to cut employees.
This is the same mistaken thinking you see from people who oppose minimum wage increases. The McDonalds down the street isn't going to cut staff because the wages went up, they need those staff to serve customers. In face the opposite can occur. The increase in money at the bottom is a huge stimulus to demand which increases traffic and requires even more staff.