I think for a lot of people, DVDs hit the spot in the same way CDs did: Quality that was good enough to never think about again.

Glossing over how CDs are at the limit of human hearing, and DVD isn’t close to the limit of vision, imagine the average person with a £300 TV across the room, using TV speakers, and maybe not wearing their glasses.
For them there isn’t that much difference getting a BD/UHD, other than occasionally noticing the 25/24hz speed up.