I went to all 4 years of high school there. The cultural shock was quite jarring, having moved from south Florida. My parents, native midwesterners, moved two years later.
People who live there remain for the same reasons people all over the country stay where they are. Usually family connections, and sheer geographic force. Most people in general end up living in the same state where they are born. Southern culture encourages this dynamic more so than in northern or western states, in my opinion.
Now, why would you want to live there if you're not from there is a completely different question, and I'd argue most people who aren't from the deep South would not enjoy living in Alabama.
Pros: Winter weather is good in most of the state. BBQ is amazing, as are many other regional dishes. if you're a foodie, you'll enjoy some time there. Low cost of living. If you're a college football fan, there's no better place (I didn't understand this at all until I went to college up north).
Cons: Beyond the surface level, southern hospitality is for natives only. Racism. Most communities are still 100% segregated, not legally of course, but culturally. If you are a white Democrat, you'll be very lonely, politically speaking. Schools and health care lag behind the nation as a whole. Debutant culture. Good ol' boy culture. Summer heat is unbearable. Birmigham city government is corrupt and bankrupt. Montgomery and Mobile not much better (Huntsville has a little different flavor due to the many transplants there working in the aerospace industry).