I go to an Endo for a couple of reasons. 1st I am more involved with my diabetes treatment and I probably know more about meds and treatment plans than the vast majority of internists (not because Im a doctor, just because I've done my homework). The Internists I've had tend to treat me like the typical diabetes patient. "Do it because I say so" and they don't really want to engage in any kind of a discussion or explanation of what they are doing for you.
So I go to an Endo that will at least treat me as an intelligent patient and will explain why he thinks I should do this or that vs. the alternatives. Secondly, I find that the Endo's have much more knowledge about the side effects and nuances of the different drugs and their interactions than the Internists do. My internist was adamant about keeping me on Avandia. My Endo put me on Byetta and took me off Avandia right away. The end result is my BS is now about 100 all the time vs never under 120 and usually over 150 with the internist.
For those of you that have good caring internists and your BS is well controlled, that is probably all the medical help you need. My situation was, I was not well controlled and my internist was not nearly as good as the Endo guy I see now. So this tells me that when things start to go from normal to worse, find a good Endo.