The point is that because of those devices and people using them, there's no need to have a console that "does it all" as well.
Now if MS had made the Xbox compareable in power to the PS4, stop being a dudebro machine, didn't come out with that online DRM and no used games nonsense, and was 400 bucks it'd be different. But even if that happened, it STILL WAS NOT GOING TO OUTSELL THE PLAYSTATION 4.
You gotta remember that Sony also owns Columbia/Sony Pictures and has Sony music. They wanted to push more people to rent/buy movies from the PS Store and get music unlimited. Inputting DLNA and music support hampers that. While I do think it's bullshyt, I'm not tripping since I got a smart TV that does this without the need of the console. and I'm not alone in this.
Bottomline is most want their consoles to be a GAMING MACHINE FIRST AND FOREMOST. And people spoke with their wallets.