Another one is medical services. There used to be a grey zone where if someone in your family got in an accident you could in practice ask for info (which hospital they're in, mostly) by phone. It could still be abused (famous people and paparazzi, for instance), but it was vital in a lot of legit cases. This is now expressly forbidden due to GDPR. If someone you know gets in an accident, it's not trivial to find out where they are (or so I've heard concerns)
@shellter I came across the results of the feature. Found a photo of my wife, scrolled up to see the photo details, and there she was being tagged as a "person" in the photo. No name of course, just an avatar. Clicking on the avatar brought up dozens of other photos she was in. In the original photo there were 5 other family members and myself, but only she got tagged. Because she's the only one who appears prominently in my gallery.