It's not super popular mainly because of its learning curve and its focus on teamplay. Notice how online English games that are super easy to play, super easy to learn, super easy to pick up and play, and super easy to get super ph4t with little effort and get super L00Tz by yourself are the popular ones.

This is saying this game is a niche game and caters to the hardcore gamers, and may be too difficult and unrewarding for a casual gamer.