>vacation is a luxury, sick days are a necessity.

In many places (Europe, generally?), vacation days are earned. At least in the Netherlands if you were absent for weeks due to illness (for which there is no fixed pool of days), and decided not to take any vacation days, you'd either have some of your vacation days rolled over to the next year or they'd be paid out to you with salary and taxed.

It's not a luxury in the slightest. You'd have earned them just as you earned your wages.