A lot of people like a sour flavor to contrast with sweet or savory, especially with fermented notes. It's why people like sourdough, cultured butter, yogurt, etc.

Personally I don't love a lot of those things; they taste spoiled to me. But I'm in a minority of "foodies", who find those flavors interesting, and find my preferred versions flat and boring. They are also very traditional flavors; that's how food was preserved before canning and leavened before baking powder and packaged yeast. De gustibus.