Outside of the Valley and New York, where there's less competition for talent, there are many companies that deduct sick days from vacation. This allows them to say that they offer 15 days (which, by US standards, is about average) of "PTO" in recruiting when it's actually less.
When companies pull that shit, you see people getting a lot sicker, because people come into the office when they should be staying home. The month of February becomes a constant, never-ending cold.