They should from both a humanitarian and long term business point of view. Ignoring the blow to employee morale, having a bunch of sick employees isn't going to help their business. And the problem is that even those willing to stay home and use their PTO/vacation/sick time could run out of time over the year. Some would then have to decide between going in sick and not getting paid which for many is not an option even if only for a few days to a week.