1. I think you forget not everyone playing is at "end game"
2. it is a bit more than "flipping a switch"
3. its very common, especially in MMO's that older content is often not used as much, if at all. I was surprised when Bozja used so much of previous areas for the relics.

they are hardly going to rewrite everything from the last 10 years because you feel a bit bored.