In places like Japan you are expected to wear a mask if you're sick, so there's no reason that shouldn't become standard in the West.
More important could be that workplaces require staff to either stay home and not infect the office when they have the flu, or wear a mask if they have to go in.
If you're a casual employee and don't have any sort of paid sick leave you either turn up or forgo the money (and potential future work). There are also those who pride themselves on never taking sick leave and "soldiering on", but invariably infect their coworkers. Here's some survey stats:
