People don't buy textbooks because they like to read. They buy them because they are required for their classes. And they can cost thousands of dollars per year.

Typically there is one specific text approved for a course, so there is a serious lack of competition. And the publishers will release new editions every year, with trivial changes, to prevent reuse of old books. It's definitely a sketchy industry, in many ways, and there is plenty of opportunity for disruption.