Few people work themselves out of a job.
Some people are paid to solve a particular problem in a set time, and at the end of that time period will be judged on how well they have solved that problem.
Over the period of their career, they will be presented with many different, but similar problems, and the success of their career depends on solving those problems.
Other people work on 'ongoing problems', which cannot be totally solved, and in which there is no set time frame for solving the problem. The success of their careers depends on making the problem look as large and as threatening as possible to attract more and more money to attempt to solve it.
In fact it is in the interests of these people to actually make the problem worse - provided they can avoid taking responsibility for doing so.
In most cases it is critical for such people to discredit objective ways of measuring success. We see teachers unions objecting vehemently to any objective measures of literacy. We see social workers producing statistics showing how badly Aborigines live, but refuse to objectively define what being Aboriginal is.
The worse they make it, the more justification they have for their actions.