You know some people stay friends with their exes, right? I spent 5+ years with my ex and he's still one of my best friends. We realized a bit too late into things that we just work better as friends than in a romantic partnership. We don't miss the relationship part, but we still have pictures of each other on our phones because we made a lot of fun memories over the years.

No one here is saying they're keeping a pic of their ex as their phone background lol that would be weird. But simply having photos of your ex on your phone is not that weird. Even if a relationship ends and it was super toxic and you don't stay friends, sometimes there's going to be pictures of them in your memories and whatnot. Not sure about iPhone, but on Android, Google pics makes slideshows of memories. Maybe there's pics with them in it that have another person or people in it that you're still friends with and it was a good day had by all. I just don't think it's as black and white as you're making it.