If you're not completing enough work because you're abusing pseudo-unlimited-PTO-via-sick-days, or you magically get a cold every Friday before a week off, that gets handled by your manager directly. But it doesn't make sense to penalize the 99% of employees who are responsible and honest.
this just sounds like a shitty situation all around. it really sucks to suspect someone / be suspected of something that can't be conclusively proven one way or the other. if you can be fired for being sick too often at convenient times, you don't really have unlimited sick leave in practice.
My point was that if performance is an issue there are ways to address that. And if enough work is getting completed, it doesn't matter how many sick days were taken (so no need to track/have a pool).
Nobody really asked or cared, so in effect they are the same thing. In practice lying was incentivized, and managers that didn't want to be lied to just adopted the policy that your sick days were yours to take for any reason.
I don't think this is something that should be legislated. It's really far down on the list to address.