That's easy. Just don't have ceilings!
Flu is caused by a virus, not by bacteria.
Wait, you mean most humans don't lick themselves already? Fascinating....
This is precisely correct. Thank you.
But to answer the question, our book circulation is actually only slightly down from what it was in the 1950s. Add in the free Internet and the video/DVD/ebook/audiobook/music CD/toy kit/puppet/etc. loans, and we are significantly above that, at least at my library.
I know you spoke tongue in cheek, but the popular image of libraries as sterile, safe places notwithstanding, in real life we deal with some surprisingly difficult-to-violent patrons, at least in the public libaries. "Front line" is not an exaggeration.
More people than you might think have something wrong that makes them sick very often. Some chronic illnesses, even without being severe, can still severely impact work attendance.
Also, I suspect that the "3 weeks of vacation and 1 or 2 weeks of sick leave" is much rarer than you think. It's unusual for front-line service-sector jobs, and almost unheard-of for minimum-wage jobs, at least in the U.S.
It might be interesting to see if there have been any studies comparing productivity for workers who are given generous, fully-compensated sick leave and workers who are given punitive sick leave such as you describe. My hunch (speaking as a supervisor and former small-business owner) is that you actually get more work out of the former and less work out of the latter -- and if my hunch is correct, then when you are sick, it actually is the employer's problem.
There are actually people who want to go to work when they're sick. They define themselves entirely by their careers, and literally have no idea how to spend their time if they aren't working.
Frankly, I think it's a mental illness.