There are actually quiet a few of us players, but we've just been busy. I'm not a pro or high level player, but I main her. Not too many people are successful playing with her offline & they drop her. Hopefully that will change soon. Then of course there's AP, Shade, Tenryuga etc.
As far as I know, Tenryuga plays her reeeaaaallly rarely.
I saw like 4 or 5 Kasumi players in that Japan tournament, lol. But she's like not too common here in the states.
I did not watch the full tournament, I've just seen some of the final fights.