I think in regards to MMOs in general, developers realized that when they didn't bake forced grouping into the design of their game that a lot of players chose to do things more on their own and interact with others on their own terms and as they wanted to. So you started seeing more options for solo progression than you had back in EQ1's day. There are still ways we can choose to be social in modern MMOs. It's just not something that the game is going to force on players.