Ah, I disagree. I think that if you are in one of those jobs and continue to justify your existence and the existence of the job, you are just reinforcing it.
For example, I know I am in one of those jobs so I tendered my resignation a few months ago and will be gone in December. Hopefully no one else fills it.
Except I am married with three kids (all under 5) and a mortgage, so it can be done. I think it's an easy cop-out to say you can't do things because of your family. Yes it's hard, and there is a lot of pressure, but if you are worth something you will make it work.
For example, I know I am in one of those jobs so I tendered my resignation a few months ago and will be gone in December. Hopefully no one else fills it.