I grew up on the east coast; sourdough is normal and tasty to me. I doubt there is any real coastal trend. San Francisco is known for sourdough bread, but it wasn't invented and spread from there.
It's very hard to find in Massachusetts grocery stores. I go out of my way to Trader Joe's to get it. When I lived in California every grocery store had piles of it.
The "Sourdough" that my normal grocery store sells isn't sourdough at all. It's shaped like Wonderbread, has the same texture as Wonderbread, and a slightly different flavor.
I got into Sourdough because it had the least amount of sugar compared to all of the other breads. When I tasted it for the first time, I was hooked.
