It was added early on at launch due to severe server congestion - literally no sooner had the game gone live that all servers became full virtually immediately, hence SE implemented this system to try and make it easier for players to actually get onto the game. For over a month after launch it literally was a case of 'go with whatever server was available' rather than 'choose a server where your friends are playing on'. Even though that level of congestion no longer happens, SE has kept it for consistency's sake.