1) Students can’t get credit for the work they do with student teams from other majors. I believe the positive intent of this is something about maintaining quality in the educational system. Because we want to make sure our students are getting what they need or expect, we develop curriculum and courses that we believe will best prepare them. This is a noble goal, but the unintended consequence is that it is difficult for our students to deviate from the prescribed courses, even if this deviation will be a better educational experience. It seems we have reduced the risk for the students, but are also reducing the potential quality or richness of their educational experience.
3) We are already so busy. Since Faculty at Cal Poly teach 2 or 3 (sometimes 4) courses per quarter, it is very difficult to find the extra time needed to plan and execute theses inter-disciplinary projects. As a teaching university our focus in on just that.