freedom. It is an extremely highly valued principle to academics. There is an organization, the American Association of University Professors, completely devoted to this. BYU has been censured by them for this.
I don't claim academic freedom is perfect, just that academics value it. Those in the "hard" sciences and engineering probably use it less, and certainly at BYU it must matter less to these faculty.
Conference schools are tied together. The values BYU promotes would be as strongly tied to the P12 schools as schools can be associated. Those who value academic freedom most do not want to be associated with a school that does not have it.
It has nothing to do with BYU forcing anything on them. But it might also have something to do with BYU's honor code, though as I said that's pretty crystal clear.