We shouldn’t punish the majority for the indiscretions of the few.
Ultimately some people will abuse sick leave, just like everything else in life. But those individuals should be dealt with on a individual basis.
Otherwise you just end up treating everyone like a criminal, at which point for an individual there’s no advantage to not engaging in abusive behaviour. You’re already effectively being punished for potential abusive behaviour, might as well make the most of it and actually engage in the abusive behaviour you’re being punished for.