DISCUSSION: Why Finish Books?

I was surfing the net as usual, reading those articles that attract my attention and I found this article about why it is not that necessary to finish reading a book and that not finishing a book does not mean you did not enjoy it or that the reader's feeling towards the book was negative. According to Tim Parks, it could even be a credit to the writer. He writes

To put a novel down before the end, then, is simply to acknowledge that for me its shape, its aesthetic quality, is in the weave of the plot and, with the best novels, in the meshing of the writing style with that weave. Style and plot, overall vision and local detail, fascinate together, in a perfect tangle. Once the structure has been set up and the narrative ball is rolling, the need for an end is just an unfortunate burden, an embarrassment, a deplorable closure of so much possibility. Sometimes I have experienced the fifty pages of suspense that so many writers feel condemned to close with as a stretch of psychological torture, obliging me to think of life as a machine for manufacturing pathos and tragedy, since the only endings we half-way believe in, of course, are the unhappy ones.

I personally cannot stand not finishing a book and even though I have abandoned some books, I had gone back to read them fully. It's not just the satisfaction of completing a book; it's not just because I want to tell people I have read this book.

What do you have to say? Should a book be necessarily finished? Will you consider your reading complete even when you did not complete? Should the reader decide when he/she thinks the book should end? Kindly share your thoughts on this.