That's slightly different though. On-demand video is probably more suited to a device that's inherently apt for it.
Cell phone: Primary use - making calls. Other features, while convenient, sometimes only make the device more cumbersome to operate.
Gaming console: Primary use - playing videogames and in some cases playing movies. It's plugged into your TV anyway, so why not expand on the services offered? Millions of people use xbox live already as it is. Plus there are still many areas that on-demand programming is not available in.