Also, you can watch YouTube on your TV and then fiddle around on your phone without being left with a floating window that both obscures your other content and is too small to see some details in the video.
Think that's more to the point. Where people watch YouTube on TV, instead of traditional channels or cable, and they are free to screw around on their smartphones. There is no telling what people are actually paying attention to, because it seems many are just running multiple devices for the sake of it. Devices are always on, then used or watched whenever something comes to mind or catches their attention.