Question: Why would "not quitting" be a headache for employers? I thought in the US you can just fire people you don't want anymore, instead of waiting for them to quit. Makes no sense to me.
First, and probably the largest motivator, is that if you fire someone without cause they will typically be able to collect on unemployment insurance which would increase the employers premiums each month.
Second, nobody likes to fire people especially if they haven't done anything wrong. Also, layoffs like this hurt the moralle of the remaining workers which could turn into too much turnover.
Having someone quit is usually preferable to increasing costs and hurting moralle, but that will not stop businesses from doing what they feel the need to do.