Maybe they should have for jobs that are physically dangerous/have a high incidence of workplace physical or mental harm. Like, say, working on a mine.

The argument goes like this:

Person A is in such a bad situation that A will accept a job that is terrible!

Prohibiting the job has a good chance of making A worse off (usually, A will accept the job if A thinks it is an improvement over the current situation)

However, we can let A accept the job, and then try to offer A even better alternatives!