Advertising cost is added to the product price. In order to generate one trillion dollars in advertising revenue, there would have to be about 20 trillion more in product spend. Civilization does not have another 20 trillion sitting around to spend.

Currently, consumers are totally bombarded with ads, on TV, on streaming, on social media, on websites. There are multiple copies of the same ad during an hour time slot. Consumers go from slight interest, to irritation, to disgust, to nauseated.

Currently, the algorithms that target ads are complete failure. At least, they could get my gender right.

The next big advance in AI is going to be ad blockers for social media, streaming video, live television. Then the next step will be bots that respond to ads, with total click through rate and messages directly to the CEO of the company. Imagine an App that calls the CEO and replays the audio of their video ad. Or an App that DM's the CEO for every social media ad. The CEO bothered a million people, let the million respond directly to the CEO.