In terms of things like "sweet tea" or Pepsi, that's very true. But having grown up in the south, and still living there, I've never known it to be commonplace to make cornbread sweet here. There's also a deep divide among southerners on whether BBQ sauce should be sweet or not.

Personally, even being from eastern NC where vinegary based BBQ rules supreme, I prefer the sweeter style of BBQ. YMMV.