Unfortunately the problem with specialized servers of any kind boils down to the cost and trouble of maintaining two separate systems. It's easy when all you have to do is turn a flag on or off (like perma-death, or open PvP as classic examples), but when you're creating a whole new set of rules like different game balance and difficulty, it can compound the difficulty in maintaining things over time. Every time they have to add something, they now have to balance it twice (or more).

Though while we're dreaming of different server types, "no duty finder" is kind of something I always wanted. The option to pick a server where the population all knows each other and has more of a community seems like something worth doing to me.