Not sure on this, but the type of job you can get in industry differs if you have a Master's or PhD... the difference between being a technician in a lab, and running a research lab, at least in my field. Also somewhat true for federal jobs. There are master's jobs, and PhD jobs.
The fields where you are bound to academia for a reasonable ROI are definitely the humanities, since there is essentially no demand for a history PhD in the private sector, or an English PhD. It can help for job hunting in an unrelated field, I guess. But, a chemistry PhD? or any other applied lab PhD, it's not like you're shooting yourself in the foot by getting an advanced degree in such a field.
The fields where you are bound to academia for a reasonable ROI are definitely the humanities, since there is essentially no demand for a history PhD in the private sector, or an English PhD. It can help for job hunting in an unrelated field, I guess. But, a chemistry PhD? or any other applied lab PhD, it's not like you're shooting yourself in the foot by getting an advanced degree in such a field.