The SEC will add only ACC schools in its region. The Big Ten is only going to add AAU schools or Notre Dame or FSU/ Miami.Still a temporary solution that exists only until the B1G/SEC comes calling. There is also incremental benefits for these schools to be associated with Stanford and Cal and play regional opponents. Blowing all that up for what is probably chump change in terms of whatever additional money the Big XII can promise in the short term is not worth it.
The BIG 12 has new contracts and is the only stable conference for the next decade outside the Big Ten or Sec.