We need to have the ability to access our retainers even in other worlds. The only two things we need is the ability to access retainer inventory and send them to venture. It is annoying when you go visit a friend's world and end up going back to your world just for a few items or once every hour to send retainers again if they want us to visit other servers to do the story or level up while the server is crowded. Crafters will need access to retainers for that reason. With the expansion coming, it would be hard for you to teleport from one server to another because the waiting time would be 20 times more than now.