School consolidation has had some influence on rivalries also, IMHO. The county I went to in high school had 10 schools during my Jr. high school days.
By my Sophomore year there were only three.
Remember the Wabash Valley Tournament? There were hundreds of schools from IN and IL as participants. I believe it was recognized as the second largest tournament in the U.S..
Just my thoughts that class competition is not the sole cause for fan interest and attendance.
Sidenote: I sat in Butler Fieldhouse as a not quite 10 yr. old and watched my Montezuma Aztecs lose to Milam and Bobby Plump. I've detested the stall strategy ever since as that is what Milam employed in the 4th quarter.
Second game was Crispus Attucks(Oscar Robertson) v.s. Muncie Central(Ron Bonham).
http://www.sycamorehoops.com/images/icons/icon7.gif