Why is the creation of OER attractive to corporations and educational institutions? OER are generally not direct revenue producers, there must be other advantages. There are a number of indirect effects for institutions and industry that stem from meaningful open source efforts, for example, they generate a strong halo effect.
MIT's OpenCourseWare provides a clear value to the MIT community. Students, even prospective students, have access to first class educational material before, during, and after taking a course.
MIT values the OpenCourseWare project as both an expression of its instructional mission, and also as a component of a feedback loop that improves the content. Their international reputation as an institution of higher learning benefits from both MIT OpenCourseWare and edX.
These projects also offer something that open source also offers corporations. A low risk method to try out a new technology, a new approach, or a new method while building an active and enthusiastic community.
Even simple things like MIT students being able to go back and watch the previous years lectures for a slightly different presentation are valuable. It can help keep you from becomming numb when repeatedly reviewing course content.