The supposition here is that it's very unfair to impose a professional cost on getting sick. I don't see it that way. I see people getting sick because they take lousy care of themselves. They're fat and eat lousy food. Also, they make various idiotic stressful choices like having a 1hr commute, or putting a kid in some germ infested day care.
People who do not make such choices rarely get sick for more than the odd few of days a year. Why should they subsidize poor choices? Not being sick a lot is a reasonable and sensible professional expectation.
I'm not sure it's "very unfair to impose a professional cost on getting sick" but we don't have a way to measure whether people are sick other than self reporting until they are way past infectious, so you're not punishing getting sick but rather reporting that you are sick, and thus encouraging under reporting, which leads to everyone getting sick more.
Not only do you still have the few odd suck days but you might also have Kids that get sick. If you use up all your vacation time then you can't take any sick days
People who do not make such choices rarely get sick for more than the odd few of days a year. Why should they subsidize poor choices? Not being sick a lot is a reasonable and sensible professional expectation.