I work an hourly programming job (not exactly the norm). I can either spend X amount of hours laminating my floor, or spend those X hours working and making money. Then I can spend a fraction of that to pay a skilled laborer to do it for me.

While not everyone has a job that's hourly, people still have a strong sense of their time's worth. Maybe working extra doesn't directly translate to X dollars at the end of the month, but it may mean you can negotiate a larger raise, or a bonus.