Because you're making the wrong assumptions. Did you not get these were social events with guests over? Do you realize how long it takes to switch activities when being social? Did you not get the fluid nature of a social event and how it was quicker and more fluid to use voice? We watch movies using Zune on the 360 because that's the only way to get 1080p/5.1. On the other system, it's bluray. It would also be Netflix if we could ever find anything to even test at that rez/quality as the press releasesstated last year. The common thread was HD viewing in a social environment, and the speed/efficiency of voice control in that environment.
But you saw the other system mentioned, even though it was merely an example of HD viewing/control, and stopped there. Fair enough, ignore the other system and replace every reference with the 360 using the controller. Exact same scenario, exact same powering up, selecting options, screensaver, but now with the offending system removed. Exact same result where it's quicker to give the voice commands.