Apple recently introduced iOS 14.5, which displays a pop-up asking users if they consent to having apps like Facebook track their online activity even when they aren't using Facebook. It turns out, most people don't want Facebook monitoring their behavior. Around the world only 13% of people have opted into being tracked. In the U.S. only 5% have opted in.
From ZDNet:
The Flurry report was compiled from aggregated insights across 2 billion mobile devices. It updates daily and ZDNet last accessed the data on Monday, 10 May 2021 at 9:30am AEST.
It also found that there are around 5% of iOS users with "restricted" app tracking, meaning apps cannot ask those users to be tracked. This figure is 3% in the US.
If users select "Ask app not to track", the app developer won't be given access to the device's advertising identifier, which is often used to collect advertising data; and apps that continue to track users that have opted out run the risk of being evicted from the App Store altogether.
