PvP content is simply easier and cheaper to produce---and has more replayability----than PVE content. What I suspect is two things: 1. Bungie just didn't have the resources to keep up with the pace of 2 DLC and a major release per year. So I think they are scaling it back to I DLC and 1 major release. 2. Most of Bungie's efforts right now are going into a major retooling of Destiny "2", because they are probably planning on dropping support for last gen consoles. So that will give them a lot more computing power to work with to add feature to the game. Since it doesn' have to be "dumbed down" (nothing personal) to fit on what are basically obsolete computers.