The argument made by advertisers and Facebook is that this is anonymized data which helps in making advertisements more relevant to people.
That works so poorly Facebook doesn't even bid on showing ads for those users currently: " And Facebook doesn’t even bid on iOS users that have Limit Ad Tracking (LAT) enabled " https://www.adexchanger.com/data-exchanges/what-do-apples-pr...
That's how anonymized data _can_ work. Of course it's also easy to mess that up and leak data about the underlying person.