Even people nominally paid hourly often cannot freely choose how many and which hours to work. (With unemployment rates as high as there are now in much of the western world, employers have more bargaining power than workers, etc.) It's not like if I got a headache this evening, I could say “rather than having a three-hour headache, I'll take this $12.50 drug which will stop it, work two hours and earn $20, and then have fun for one hour”.