Partly the performance, partly the declining population, partly it's just not very good pvp. Nowadays everyone's running in circles at 200%, jiggling around behind boxes, or playing hide and seek... Get's old. Haven't been in since early November though so maybe things have improved. When it worked, and you actually got a fight though, it was good. And, as other's have said, I found the pvp community frendlier than the pve. Less pulling out your dps and measuring it anyway.