Second hand DVDs are not very cheap in second hand shops
They're ridiculously cheap. Round here, half a Euro for a CD and a Euro for a DVD which will have cost significantly more. That's cheap enough to pick up a handful, watch them, and take them back to the shop next week if you don't want to keep them - keep the goodness going around and help the charity too. What's not to like?
Why? I guess because, hey, everything's streaming now, granddad. You want a Dolby with that?
But some of us remember that unless the medium is in your hand (or on your shelf) you're playing it at someone else's pleasure...