Why does conference expansion HAVE to include 16 teams??

What is so magical and necessary about the major conferences expanding to 16 "super conferences". All you hear anyone talk about is four 16 team super conferences. Why not five 14 team conferences instead? 16 SEC teams will totally destroy a lot of long time cross divisional rivalry games and totally destroy any decent OOC schedules. Let`s add A&M to the SEC West and either Va Tech, UNC, FSU, or NC State to the SEC East and be done with expansion for good. Frick all this going to 16 business. It isn`t like the new conferences are going to leave the SEC out of a playoff if we only have 14 teams instead of 16.