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.
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.