Well... sports take a lot of dedication and it's usually bound to certain parameters — rules, team sizes, tactics. In this scenario it doesn't serve much of a longterm purpose either, aside from exercise and a way to spend the time of course. There are no tournaments and with the frequency that we lose people here, even keeping the teams together must be difficult.
Compare that to the Defense Force that works towards a goal that benefits us all or even looser formed clubs that aren't as dependent on keeping its members.