a. the servers aren't empty, that's just a BS complaint by people that don't understand the concept that other players might be interested in doing something other than what the complainer is interested in at that moment.

b. the server load isn't the player-at least not much-its the extra Area and all the mobs in it that eats resources. SE just isn't interested in putting in the equipment to handle the load, much like they have no interest in making the game compatible with modern software/hardware (direct x/graphics card drivers/multi-processor systems, etc.)