FB advertising is a walled garden and they want advertisers to come to FB to buy ad space. They would never simply sell that data back out in to the broader ecosystem. It's not about charity, it's about control.
Also, the business model allows Facebook and Google to talk about protecting your data... while also reaping the advantage of retaining sole access to that data.
By selling targeting only, advertisers are forced to buy again and again.
If they sold the underlying data, they'd be cheapening their own treasure.
"Selling" user data isn't legal without a basis under GDPR and they don't have it. Also, Meta aren't stupid to give away their asset to others. Like Google, they don't actually sell user data, rather they provide an ads platform on which people can place bids. Which under GDPR is also unlawful, and Meta just found out about it.
Granted, you may believe that they'll engage in unlawful behavior anyway, but I'd say that they are a huge target, breaking records in fines which are only growing.
Well, they didn't just find about it, they knew about it from the very beginning and employed every trick in the book to weasel out of it.
https://www.theregister.com/2023/08/02/meta_eu_gdpr_advertis...
It is only after they got slapped with multiple costly fines this year that they now pretend to change their tune.