A great database guy is a boon for a development team. Don't take one for granted. When he is gone, you will feel the pain. I've worked on big projects with a good one and with lackluster talent. Let me tell you, developer productivity goes down hill fast in the latter situation.
I suspect it is a matter of specialization. There isn't much a DBA can do that I can't do; however, there is very little a DBA does that I want todo. And it is a total break in mindset to go from solving problems via Object Oriented constructs to solving them with set theory and the less then impressive tools available for integrating with transactional databases.