Twitch is a streaming service, not a video hosting service. The amount of views the vast majority of vods get on Twitch is abysmal, and by default those vods are only kept for a minimal amount of time.

Youtube is attempting to move into Twitch’s space with live-streaming, but Twitch is certainly not competing with youtube as a video hosting product. Vimeo is the primary competitor there, and I have no idea how good a job they’re doing really.