To receive the lowest commercial price on the digital course materials specified by your instructor, and in order for you to be prepared for your classes, UT and the Co-op have made them available to you through Canvas on or before the first class day.
Other schools using a similar system report that over 95% of students choose to remain opted in to their course materials. Because of this high participation rate, it is much easier for students, and the Co-op, if everyone is opted in by default but given the option to opt out. The high participation rate is also an incentive for publishers to offer lower prices, and a model in which students are opted in by default is generally a condition for getting the very best prices from publishers because it leads to higher participation rates by students.