I've been entertaining that view for a long time now wrt. advertising, but what other service job has the same characteristics? Namely, that your works serves mostly to undo the results of your peers' work, and vice versa?

I think medical insurance has a component like this. The doctor's office has people in it whose job is to make sure that the doctor gets paid, and the insurance company's office has people in it who try to find ways to not pay.

There are vast numbers of government (and quasi-government) employees who work to cancel or mitigate the actions of other government employees.