I was a kid not too long ago and no one gave a shit about a single luxury item other than iPhones. People who had fancy stuff were generally made fun of, the cool kids all wore stuff from the thrift store
The point is that there will always be something that kids use to single out and ostracize others. Kids are little barbarians who don't know how to be decent human beings yet, it isn't going to change just because they have to pick on some other characteristic to mock.
Why does apple ahve to encourage that behavior though? Theyve designed iMessage to make the experience worse with some people, it absolutely encourages exclusionary behavior among those who arent inclined to be exclusionary. Obviously some kids are just assholes, but plenty arent just going around looking for things to be mean about.