IMO, many people mistakenly think that people upgraded from VHS to DVD due to image quality... they didn't.
People upgraded from VHS to DVD because DVD offers extra features (documentaries, subtitles in several languages etc), durability, menus and ease of use (no more rewinding). Picture quality was also a factor, but a small one.
Blu-Ray over DVD only offers better picture quality. Most people don't care, certainly not enough to justify buying a new player and 30-50% more expensive movies.
My Mario Kart Wii friend code: 2707-1866-0957