you do not get unemployment if you quit your job voluntarily. when managers say employees leave in order to collect unemployment, it's a lie.
Since they were fired, they got unemployment. Now, restaurants are open again, but folks don't want to go back for the meager pay (and likely the extra freedom in their time is welcome as well).
but anyway, for those who do collect unemployment, job search requirements are in effect now. unemployment offices are requiring workers to apply to jobs and document their search. they cross-reference with employers and will actually revoke unemployment if job offers are declined. if restaurants still can't hire staff under these forced conditions, it's because they are simply worse than other jobs available, and perhaps even worse than no income.