But the missing part is "we know they need this!" but they don't have the ad network to have the pixels on the vendor sites to track the conversion (or not for remarketing!). They only have half (at most) of the picture. This is why they tried to create a browser (remember that? Nope me neither) to try and get the full picture.

Advertisers are accustomed to pay for conversions now. If you can't track it, you cant prove it happened.

Open ai will need to spin up the entire infrastructure (Inc sales teams, support teams, servers etc) to run the ad network. Not impossible but it is a big lift and they're already burning money.

Their best bet is probably to just sign up for selling their ad space with Google, like all the other apps and websites do