What I have seen is when contractors become permanent, sickness suddenly increases.
As a contractor forever, I recall taking 6 sick leave in last 20+ years as I don't get paid if I don't work.
You need a moral high trust society for things to work well.
Otherwise you have people come in sick because they're either afraid of losing their job or don't want to not be paid. This is not good for obvious reasons. If you do protected sick leave you then have some people abuse the system and call in sick for babalaas. You could eventually weed these people out, but after some losses.