First of all, reading traditional books is a habit or a way of life for many people, which is completely different from the feeling of electronic reading. Moreover, compared with e-books, paper books have unique advantages: easy to find, comfortable to read and easy to take notes.
E-books can't read professional books well, even if the PDF format is convenient for you to read, it is a big problem, and because of copyright and time problems, many things can't be found in electronic version at all.