If I’m watching a let's play on YouTube, I don't care about buying crayola crayons. If you’d present me an ad for the game the player plays, on the other hand, I’d probably buy it. Maybe even give the youtuber like a 2% cut of the sales.
The best kind of advertising is invisible to those uninterested and visible to those that stand to benefit from the offer. Most good online advertising systems are incentivized towards that, but then schools incentivize towards good grades, and they don't produce one examplary student after another.
Part of the problem may be the esteem of the profession. No kid tells himself "I want to work on PPC optimization and better Ad Targeting". It's a terrible pity a profession that handles informing consumers about goods offered is so shrouded in ignorance. How many brilliant products designed by even more brilliant engineers failed in the cradle because nobody ever found out about them, or the ones that did couldn't make out their use? Because when you build a better mousetrap...you've got a better mousetrap and the world keeps using the ones they have.
Also that 2% cut of sales would be there if the youtuber were to post an affiliate link.
And it won't neccesairily lead to less obtrusive advertising.
Useless products seems a little harsh, since a truly useless product wouldn't survive for long. You might view them as useless, but then a high schooler might not know what to do with a cisco rack, and say the same thing. Which means cisco shouldn't advertise their products to highschoolers (for the most part).
Google Ads based on browsing behaviour only try to sell you stuff that you already bought and no longer need. By the point the ad shows you graphics cards, like for me right now, I already bought one. When I was searching for one, the ads were showing me crayola crayons instead.
Make relevant ads based on what the person needs right now. No need for cookies or any tracking.
