The Scholarly Publishing and Academic Resources Coalition (SPARC) summarizes the why behind using OER with these four points:
Textbook costs should not be a barrier to education
Students learn more when they have access to quality materials
Technology holds boundless potential to improve teaching and learning
Better education means a better future
OER supports a future where:
Students and instructors have free access to a wide variety of high-quality educational resources that have been collaboratively developed, reviewed, revised, and shared across institutions
Educational resources can be easily adapted to fit within the context of specific courses, and to meet the needs of specific students
The cost of creation, use, and maintenance of curricular materials is much lower than the current costs of traditional textbooks and other classroom resources