Aikar explained this a few pages ago but basically because; 1) To reduce the confusion that a new world would create 2) Just to make each world a little more specific when mentioned e.g. So instead of "let's go to the Wild" and the response being "which wild?" It would be "let's go to the Frontier" and "alright" as the names "Frontier" and "Wastelands" would be pretty much separated.
Please only Aikar respond, because I am being told different things. Will there be a 1.5 Wild/Frontier reset?