Earlier quoted context omitted.
The fact that we as in industry and we as citizens of free nations do not end these operations, terminate their corporate charters and throw the responsible in jail is indicator #1 that freedom (not the GOP free-dumb) as we know it is in it's death rattle.
Why are people using the facebook sdk? What does it give them?
1. It is required for a "login with Facebook" feature, apparently. I'd presume this goes for other feautures that integrate with facebook, such as "invite from your friends" or "share on facebook(messenger)".
2. It gives access to metrics, when added to your own, greatly enrich your own data collection.
3. It is required when working with Facebook ads - though I would not know how this ties in with mobile apps: on web it is clearer (where you are required to host "the pixel" on your website in order to have ads on facebook link to that website.)
4. It is feature rich, so as a pure SDK, it offers neat utilities; though for each of these, there are better alternatives found in separate libs.