From a UConn fan's perspective, why in the world would Notre Dame not want to be a full member of the B1G? What is the difference between the revenue generated from their current deal with NBC and what the Big Ten Network currently generates for it's members?
If you move to the B1G, they can resume your rivalries with Michigan, Michigan State, Purdue etc while making geographical sense for their Olympic sports teams. Set up OOC games with Boston College and USC for the next 20+ years and that takes care of the "national schedule" on the football side.
Lots of reasons, in pretty much order of importance:
1) Historical hatred of the Big Ten by ND (and visa versa);
2) ND wants to stay out of a football conference;
3) ND wants to play more Southern and Western games for recruiting;
4) ND believes that the Big Ten "regionalizes" them to the Midwest/Mid-Atlantic;
5) Poor mix of schools. All except Northwestern are huge public land grant schools;
6) ND feels the Big Ten is run pretty much for the benefit of Ohio State and Michigan;
7) ND would make more money from the Big Ten, but lose exposure of OTA network (NBC);
8) A 9 game Big Ten schedule plus Navy, Stanford and Southern Cal leaves no room for Shamrock Series games nor big name series like Texas, Oklahoma, Arizona State, Georgia, etc..
My guess is that if a football conference membership was inevitable for ND, a poll of ND fans would find the ACC favored over the Big Ten by a huge margin.
Not many ND people are that fond of the Big Ten, most want the Irish to never have anything to do with that conference. That enmity is decades old and is in no danger of subsiding.
For ND, joining the Big Ten Conference would be like the Americans surrendering to the Japanese on Bataan. The Big Ten has always been the enemy for ND.
It would pretty much be the worst case scenario for ND in the reality of P5 conference realignment.
Every move that ND has made since 1991 (NBC contract, Big East membership, ACC membership, etc..) has mostly been made to keep football independent and out of the clutches of the Big Ten.