I used to feel like I had to finish it. Like if I didn't finish the book I'd miss something, or I'd be a quitter. Then I read the Earth's Children series, and I just. Couldn't. Finish. Putting it down was so LIBERATING!!!! I couldn't read another page of hardened members or moist mounds interspersed with mind numbingly boring geological descriptions. It's the only book I ever stopped reading but I won't be afraid to do it again!
No way would I finish a book that has lost my attention.
My time is precious, and not for book's that will not keep me interested.
I don't know 'why' more people stick with it....only to be quite disappointed, after it is read!