While Twitch.TV is soaring in popularity, it is ironic that the familiarly named Twitch gaming style is fading away.
Twitch gaming is a way of playing a videogame that employs the maximum use of the players ability to react to and read scenarios. It is a bit like playing at a professional level in tennis, compared to playing at a leisure club. It simply demands more human ability.
Multiplayer first person shooters classically encouraged this type of gameplay. Many of which were specifically designed around the fact that people would play the game and expect to play the game this way.
However, as videogames become more mainstream, we see a gradual dampening in the average ability of human players. As something becomes more popular, it becomes more mediocre to appeal to the lowered skill level and the growing market.
There are a few twitch games still going strong. CS:GO and the new Unreal Tournament are classic twitch shooters, with their roots in that old era of PC FPS.
Perhaps we will see a resurgence if the skill level of the average gamer increases. It is hard to tell.