If you go down that road... then why not give people who eat healthier more vacation days? How about those who don't drink alcohol? How about drive safer? How about don't get pregnant? It would be pretty hard to draw a line and put some people and some habits on the penalize side of it.
I honestly would love if most jobs switched to paying by productivity. Then you can have any habits you want... as long as you are productive. You get paid for what you do. For all the other time you spend doing other things and not producing anything, you don't get paid. You can do what you want with your time.
I personally think 'sick' days are stupid. Pay me for the days I work. Don't pay me for the days I don't work.
OK, what about the person who has a congenital defect and is frequently seriously ill? (not their fault)
What about parents who have kids who are sick?
What about women who have children (unless you want the human race to be extinct in within 100 years)?
What people who have accidents and are seriously injured, and no longer able to work? (accidents can be your fault, or not)
For the record, there are plenty of jobs that "pay by productivity". Any job that doesn't have paid time off. How has that worked out for individuals and society?
I think we could use insurance to cover most of the situations you mention. Whether someone has a situation that prevents them from working and it's their fault, or not their fault, is the employer really on the hook to pay them when they're not working? Where does that pay come from? Or do we just assume all these companies are 'rich' so they should give us money?
What if I'm a self-employed, sole employee at my company...then I get pregnant, need some time off near/after the birth...who pays me to not work? Or do I have to accept that for the time I don't work, I won't be paid?
What if I'm in a small company with two employees and I have a health condition that prevents me from working for months... who pays me to not work then? Basically the second employee would have to bring in enough profit to cover both their pay and mine. Yay for me, shit for them.
Three employee company? Four? At what point is it ok for someone unable to work to collect a paycheck (not an insurance payment) funded by the other workers? This isn't economically feasible.
I'd like to see it more common that you can take 'sick' days, but they're unpaid. What if I work all year and I earn 5 sick days... so I've pretty much earned 370 days of pay but only get paid 365 days worth. If I don't use those days I'm losing pay I earned. With the way people are today, some folks can't afford a system like that. Save money? Have an emergency fund? Put extra food in the pantry today so that I can eat next week even if I don't have a paycheck?! Madness I say! You can't expect me to earn a living, companies owe me a paycheck for not working!
That being said, because our system is jacked up, I will always take EVERY SINGLE sick day that I earned, whether or not I need them. I earned those days worth of pay, so I will damn sure collect those days worth of pay.