IIRC they actually don't and it materially reduced Meta's profit when Apple rolled out the advertiser ID system.

"Facebook says Apple iOS privacy change will result in $10 billion revenue hit this year" (2022):

* https://www.cnbc.com/2022/02/02/facebook-says-apple-ios-priv...

See also perhaps "It’s not Meta - its APPLE who have screwed us small advertisers":

* https://www.reddit.com/r/FacebookAds/comments/1o85w2q/

Wow that number is line an order of magnitude or more than I expected it would be

Won't someone please think of the poor advertisers? /s

I would be even more shocked if instead of adapting, they’ve continued to lose $10b a year

That may have been true initially but meta has enough information to heuristically observe unidentified users and compare their behaviors with known consumers. It only takes a few actions to uniquely identify a consumer with a high degree of confidence.

Yes, it was temporary and Meta revenue and profit at all time high (before data center buildout).

Pretty sure Meta doesn't do that on iOS devices because that'll get you banned from the App Store. They just figured out ways to not need individual fingerprinting.

Apple does not enforce the rules uniformly