I suspect enabling the IDFA (and asking users for permission to track) is pushed by Facebook and similar user-tracking platforms for their own benefit. At the same time, each app doesn't have any incentives to enable IDFA and show the much hated and spooky ATT popup.

Here's what I think happens: IDFA helps Facebook "connect the dots" and know which apps are installed on which devices. When you run FB ads for your app, Facebook looks for some good audiences using the information it has on users, including the apps already installed on their devices, where IDFA is hopefully enabled.

This has nothing to do with your app. So, once it finds its user and gets installed on their device, it is now used by Facebook to further improve knowledge about the given user and help other apps find their audiences, which has nothing to do with you.

Is my hypothesis correct?

Let alone, according to some stats, 60-70% of users say No to tracking anyway, which makes the whole thing even more pointless in my opinion.

Would be great to hear the opinions of some knowledgeable people. Thanks!