At one point in time, I was considering getting a JD-MBA. During my last internship, I met a number of people who had gotten the joint degree and asked them what their perspective/opinion was.
Every single one of them told me that, in the long run, they didn't see the usefulness of getting both degrees. The reason they gave me was that, in their own career paths, they find themselves using only one of the two degrees.
I'm not saying this is necessarily true in every situation, but it had a lot to do with my decision not to pursue a joint degree.