I think the main issue is that people ge excited about a topic and buy the book. They enjoy few chapters but soon they come across something more interesting on

I think the main issue is that people ge excited about a topic and buy the book. They enjoy few chapters but soon they come across something more interesting on internet and then buy that book too. Almost all non-fiction has some boring bits which you just have to struggle through to reach interesting parts. Its in this struggle stage I find myself most vulnerable to start reading another book and leaving the current one. Do this for years and you end up having lots of unread books. I thought this is what OP was referring to.