The only thing stopping them doing this right now, is that they know it would get regulatory pushback. It has a real chance of causing laws to be made about when and how advertising is appropriate, and those laws might stop some of the things they're doing now. So they sit as close to that line as they can without crossing it so they can keep self-regulation.

The moment they believe world governments wouldn't stop them doing it, is the moment they'll do it.

And in terms of benefit for the advertisers and service providers, it's a no-brainer. Advertisers know that a large percentage of people tune out, or even leave the room when an advert is on. I think it's part of the reason they kept them so short on youtube, because if they showed you that there's 1:30 ad break you might go to the toilet, get a drink, or anything else that takes you away from the ad. If they show you 15seconds, well you'll probably just sit that one out.

An advert they know people are actually watching is worth a LOT more to advertisers.