A lot of terrible jobs are required in our society to be done by people from negative encouragement. The belief that all jobs can be done purely through positive encouragement I think is potentially naive. Maybe nurse was a bad example but people who work from this negative encouragement are in many ways "forced" to.
For illustration some of the worst farm labor jobs in America are done by illegal immigrants, and it's not obvious legal citizens would do those jobs at any rate that makes economic sense. The economic engine that gets us food in our grocery store runs on their desperation.