The whole trick of designing institutions is to make sure that when they act for their own self-preservation (as they will and do) they will simultaneously be achieving the goal we want them to be achieving.
The problem is we've somehow managed to create organizations that continue to exist even when they completely fail to accomplish the intended tasks. Once your method of self-preservation shifts from "functioning" to "lobbying", the whole thing needs to be dismantled.
The TSA is fortunate in that they have other people lobbying on their behalf, but that doesn't change the fact that they exist due to legislation rather than effectiveness.