Ever try flying sticky kites whilst all around you are power kites? I guess we are afraid we'll get overwhelmed just like we do on the field. Sticky kites need hemispheres, power kites need corridors (runways?).
I like that explanation - never thought of it like that.
I do this quite a bit at SEKA get togethers you get a fair mix of kites, though mainly traction as Roy said. Generally the guys flying traction do tend to launch then clutter off so I fly at the set-out area and it's not too much of a problem. A lot of them fly Revs anyway, but oddly there's only a couple of us who fly two line sport kites for some reason.