It still seems unnecessary to do it that way though. Say you give employees a 2 week notice, exactly the same time you'd want an employee to give you a heads up that they were leaving. What are the odds a huge portion of your staff quits en masse to the point where you couldn't even operate for the final 2 weeks? In all likelihood, wouldn't most of them start looking for a new job then but stay on for the final 2 weeks, then start working somewhere else after the restaurant closed? And even if they all did quit, why not shut it down a couple weeks earlier than expected? Does it really make that big a difference?
I know the restaurant/bar workforce is very transient and has a gigantic amount of turnover, but I can't imagine they'd all just quit immediately if given a couple weeks notice, even though they probably pretty easily could find another job. Maybe they would, I don't know.