Again, I'm not talking specifically about Rift. I also don't believe I said WoW is unique, only merely use it in examples because many games seem to try and copy it specifically given that it has the largest following.
Anyways, I'm going to conclude my point simply by saying that developers should be looking to create features in the hopes that they become a new standard. When new standards are achieved, the core functionality of something is permanently improved and therefore can further be expanded upon. If no one can make changes that stick the core functionality will always remain the same. Going back to the car brown townogy, ten or so years ago it was a premium feature to have security and power locks, now it's pretty much standard.