I think they just want to show you ads and help you buy stuff. The incentive is actually to keep the data to themselves so they can monetize access to it via ads.

The shopping experience is significantly less hostile than Amazon’s 1P digital storefront and I kinda don’t care if fb knows that I want to buy a computer.

The only thing to worry about is that they want you to install a native app. But this UX would be difficult to provide for free via the web due to the obvious abuse potential of giving free access to LLMs + remote compute + browser and tool use. And I think as long as you use it to shop or automate web tasks (and give them access to the top of funnel for customer intent, the $300B/yr thing Google monetizes) they don’t really have any reason to abuse your data.