I tend to buy and DVD that interests me, and I'll quite happily make a "blind buy" (something most people seem to be against) because it's just to expensive for us to go to the cinema to see films. Too be honest buying a DVD may be slightly more expensive (but only slightly) but I always work on the assumption that I can sell unwanted DVDs later and get some of the money back. But in practice I've only sold a few DVDs - the number can be counted on the fingers of both hands.
There are a few Disney DVDs that I have bought that I otherwise wouldn't (such as the two Kim Possible DVDs) but I only got them as they were cheap. I get very few Disney live-action films.
We won't mention my International Disney DVD duplicates. At least I've vowed not to buy a Lion King Trilogy - I have enough Lion King DVDs all ready! (And I think its a pretty poor disc as regards to the supplements!

) Still, to repeat my catchphrase "It's better than collecting Disney Snow Globes". If I tell myself that enough times, I may think it's true!
As for the question of buying DVDs because I think I should - well, yes, I do. While I know Schindler's List is an exceptional film, I don't really see myself watching it that many times. But I have this strange collecting obsession so not only do I want it, I want "the best version available" so I've got the gift set on order. But the vast majority of the films I buy are for content I want to see (even if sometimes it takes me about 4 months to finally see it).