Simple supply and demand
Demand for new workers increases due to old workers leaving, which happens naturally, but has been happening more for a variety of generally Corona-related reasons (like disproportionately high risk of infection compared to other, non-service jobs, or increased pressure from additional work they have to perform heightening burnout).
Normally, there would be a supply of new workers to fill that demand. However, these same Covid-related reasons (along with unemployment beginning to pay more than the legal fucking minimum wage) are also contributing to workers not being willing or able to (re)enter said positions, thereby lowering the supply.
In any other situation, anyone with even a rudimentary understanding of finance could see that; (increased demand) + (decreased supply) = (raised costs of acquisition) and act accordingly. But since it's jobs, that means it's somehow "different," and instead of raising wages, people do shit like this:

Which sounds fine, unless you know that going in for that interview and not accepting whatever "offer" they decide to spit on your face will allow that employer to, if they're feeling spiteful, potentially report to Unemployment that you're refusing employment, which could then result in you losing said unemployment.
And that risk isn't worth $50.

T-posing wagie asserting his dominance over would-be employers