"it seems that the pinnacle of human intelligence: the greatest, smartest, brightest minds have all come together to... build us another ad engine"

Putting aside the ridiculous hyperbole, the reason is that consumerism is our culture. Our cult-ure. Everything is oriented toward and reduced to consumption. Our worth as human beings is replaced by consumerist criteria and measures. It's why physicists leave research and work in finance where their training is repurposed in service of all sorts of financial jiggery-pokery.

"The A in AGI stands for Ads! It's all ads!! Ads that you can't even block because they are BAKED into the streamed probabilistic word selector purposefully skewed to output the highest bidder's marketing copy."

But note the implication. Sure, ads weaved into the content, but they still must be targeted. And here's the irony of the online existence. People often refrain from expressing various desires in public for fear of judgement. It's why the vitriol online is so much spicier. The world of social media where you can express repressed opinions, the world of games and other ahem media where you can sublimate all sorts of desires and fantasies - all of this is data for the AI machine. These companies, in some respects, "know" you better than the people in your life do - especially those parts of you that you could be embarrassed to reveal in public - and they use this information to manipulate you, largely for profit, but why not for broader social and psychological control. AI's convenience is already irresistible. It's the go-to in Google search.