I was going to say that as well. I think the Deep specialty is of particular value in that many charters do dives routinely below 100'. I always wondered about a DM leading such dives if they weren't Deep certified.
...or at least have been there before.
I have had DM candidates who have never been close to 100 feet deep. I believe you have to be thoroughly comfortable with such depths if you are to be expected to be able to deal with anything that develops on such a dive.