There are obviously a lot of factors that go into the decision making process of whether you should take a particular job at a particular wage. But at least two are 1) how much you're getting otherwise from other sources, and 2) competition from other sources of labor.
For 2, consider this: https://www.dhs.gov/immigration-statistics/special-reports/l...
New entries in Q4 2020 down 78% from the year before, and that's on top of a general downward trend in net immigration to the US that's been happening for a decade. Is this temporary because of Covid? Probably. But immigration at the low end of the wage scale is a factor that drives down the wages. Anyone who has ever lived in an apartment complex in Santa Ana and seen neighbors with 14 people packed into a 3 bedroom apartment understands why. Native born Americans simply aren't willing to live like that. The expectation for what constitutes a baseline reasonable lifestyle isn't the same.
For 1, these comments about "experimenting with UBI" or freeloaders living off the government seem to miss the point that augmented benefits are a temporary pandemic relief measure. Of course the low end of the labor market is abnormally depressed right now. That is on purpose as part of a calculated, intentional public health response making it easier for people to decide not to work. Lo and behold, many are now actually making that decision.
For some reason, there seems to be this widespread notion that this is a permanent change, but it isn't. You're still not technically allowed to just quit or refuse to work because you want unemployment, but go ahead and look at the actual description of what constitutes a Covid-related reason to apply for relief: https://wdr.doleta.gov/directives/attach/UIPL/UIPL_16-20.pdf
If your place of employment was closed, if your kid's school was closed, if you were ever diagnosed, had symptoms, were quarantined, or anyone in your family was, your head of household died, you need to care for some who was diagnosed. None of those are usually reasons you're allowed to claim unemployment benefits. Now they are.
How long will this go on? Who knows, but definitely not forever. This is also the answer to why businesses don't just offer more. Prices are subject to a ratchet effect. Offer more now to overcome the inertia of people choosing to stay unemployed during an abnormally favorable time to be unemployed and you're very likely to have to permanently pay higher wages even when the enhanced benefits are gone. Businesses are getting relief, too, and are willing to gamble that they can wait long enough for wages to come back down.