It's not there, go to the Web! Hohoha

Any idea why some textbooks especially those used in universities make some of their content available through the web, not included in the book? What's the point? I cannot see adding extra less than 100 pages an issue.

 

Sorry for not wording my question properly. I meant to ask that some chapters/sections of books are not included in the hard copy version, and readers have to go to the book's website to get the missing content. Though the content is listed in the book TOC, it's made available only online.

 

Well makes sense to keep the cost lower than it would be with those extensions. But it's becoming a fashion all authors using it. I could name some books but I don't want to make them look bad...so I will stay general. One book is less than 500 pages yet it contains several chapters which I consider important to be there. The book in the end could be used in advanced courses, by non students as a reference...etc. Nonetheless the books is super expensive at least for its size.
My guess here the authors, which are professors, want the readers somehow to reach their websites, which are very likely universities' websites...sort of advertisement??? Could be far from truth but I still cannot see how less than 10% of the book size will make the price much higher. It's already high.
I'm worried here because when knowledge becomes a business then it's in danger. Exactly like with any other product, the quality goes down.

 

I've a better idea for authors. What about instead of embedding screenshots of a computer software and its script...they could make this stuff available online and have the more related chapters printed on paper. :-) Software changes faster than the core subject of the book especially if it's math or physics related. So lets make more sense of the extremely expensive books.