Also at least in my country I can call in sick if I have a headache, will be paid for the day and there is no number of paid-time-off-days, which will be subtracted by one when I do so. The employer continues to pay up to 6 weeks of salary if you need to stay at home due to sickness, and for a period longer than 3 days you need a dr to confirm you're sick. The number of sick days per year depend on you actually being sick - I was baffled when I learned this is a fixed number in the US (at least for some) .
I guess the motivation to work sick when you have a limited number of paid sick days also contributes to the usage of pain killers.