Well, watching a DVD on a (fairly) large screen really shows differences between a DVD rip on a regular single layer DVD disk, and the original. I want the best possible picture quality while watching a movie in my home theater. Watching on a regular TV set does not show much difference, but once to you go into larger sized screens you see a difference. And it annoys the hell out of me.
So, by going down from 3-8GB of data to a 4GB movie, I save about 1€. I am willing to pay this price to get the best quality possible.