Before the interstate system, the US highway system was made up of the better roads, and US29 was one of the major ones. Almost all the original ACC schools were either on US 29 or an hour or so from US 29 via a US highway road. The SEC original configuration was actually pretty compact when you see where the schools were located on the map. Same for the Big 10 with Minnesota being an outlier, the Big 8 with Colorado being an outlier, and the Southwestern Conference with Arkansas being an outlier. The conferences were set up originally for bus travel, but with plane travel these days, the schools can work out deals with the airlines to get some pretty cheap flights for their non revenue sports. So, a nationwide conference probably doesn't increase those costs too much.