nmltprand's comments

If they get a match with a high school picture for "John Smith" from a school in an affluent area, they can adjust advertisements.

If your face appears in a riot, they can resell the information to the government.

They want your selfies for facial recognition in order to track you better across the web and possibly resell that information to third parties.

Also a great dataset for "AI" training, so your face can appear in modified form in laundered pictures.