The first AI company to cram their product full of ads will get roasted over the coals for it. My guess is they're all playing chicken and waiting to be the second to do it. I'd also guess that they're all already thinking about ways to introduce it that will generate the least backlash.

Google could do it in 2000 because their search was legitimately so much better, and also because their ads were comparatively more relevant and unobtrusive than modern ads. In comparison, LLMs are relatively similar in performance unless you're picky enough that you're probably already paying and thus wouldn't be in the ad-supported tier.

That said, I wonder if ads are even lucrative enough to move the needle relative to how much training costs are increasing with each generation.