This sounds true if you have a choice of jobs. But with "regular" jobs, we accept that someone can be forced by circumstances to take such a job, even if it isn't the greatest job in the world.
Suppose a friend of mine is unemployed and complaining about money problems, I can imagine myself saying "So why don't you just take the job of a dishwasher until things get better?"
But I can't really imagine myself saying "So why don't you just sell your body until things get better?"