jammindude, I think you nailed it earlier when you said he was regional. There are just some cities where he was and still is huge. I live in one of them (St. Louis).
Let me put it this way: every year during the NCAA tournament, KSHE-95 (our local hard rock radio station) does a bracket where fans get to vote for the best band, and the winner is always Rush (they are huge here, too), Zeppelin, Floyd or solo Sammy Hagar. Hagar has won it more than once. Think about that: Sammy Hagar being voted by fans as being better than Rush or LZ or Floyd. Sound crazy, but it just shows how popular he is here. KSHE was on board with him since the 70s, and Hagar has often spoke glowingly about both STL and KSHE.