I think fighting games are a niche market as it is, putting it on the PC just doesn't seem right and further limits the potential for profit. Video games you have to remember are a product first.
The best fighting games were the arcade joystick ones and naturally it just evolved better on consoles then with a keyboard and mouse man.
Try picturing super smash bros and playing Tekken Tag on a keyboard and mouse, kinda ruins it.
You also have to think, is the average gamer going to run out and buy a joystick setup for their PC just to enjoy a fighting game or are they going to get it for their Xbox which already has a very enjoyable controller for fighting games?