Why would you use an accent when it actively gets you associated with idiots / racists / conservatives?

There's a lot of people who have been hurt by Southern culture, so naturally they reject that accent. A lot of decent people reject the accent because they don't want people to assume they're one of those Southerners. There's also the aspect that you end up talking to people outside your region a lot more often than in the old days, so you learn to switch it off because people outside your region might not understand you well.