1) Youtube isn't profitable, but it's taking more and more "hours watched" out of the TV market. Google can keep it running at break even for as long as they want, and then adjust the ad prices up very, very slightly and start making profit based on the huge audience.
2) Video watching (usually) has very little commercial intent, especially in terms of some kind of "commercial value per byte served" measure. This compares very badly to Pinterest, where a very significant amount of usage has almost direct purchase intent.
