You don't need a license for most of what people do with traditional, physical copyrighted copies of works: read them, play a DVD at home, etc. Those things are outside the scope of copyright. But you do need a license to make copies, and ebooks generally come with licensing agreements, again because to read an ebook, you must first make a brand new copy of it. Anyway as a result physical books just don't have "licenses" to begin with and if they tried they'd be unenforceable, since you don't need to "agree" to any "terms" to read a book.