I think part of the problem is - while we might all consider ourselves "big ten fans" there is no way I'm watching, say, Northwestern v. Purdue on the BTN when I can watch a game like Georgia Florida, or whatever the major networks (or even ESPN) has on at the same time.
That's the same problem the "ESPN + game of the week" has... who the hell wants to see Indiana v. Illinois - save for Illinois and Indiana fans? No one. So.... getting back to BTN - teams that carry big fanbases -
OSU, PSU, Michigan.. the BTN ratings will be good when those games are on regardless of opponant. But, no
OSU fan (Ok, FEW) are skipping Texas Oklahoma to see Michigan State knock heads with Minnesota.