re: Why does the SEC keep Vandy?

Well, it leads to cedibility of the league, and Vanderbilt is a charter member of the SEC. Only they can decide to leave, and that's not going to happen. They were also the winningest SEC football program until the 1960s, when Alabama passed them. Regardless, GT had their chance, and they left. If a team were to be added, I would want it to be them, but I don't see the format changing.