It is pretty rare for my partners to date each other, so most breakups are usually โnormalโ. Even when they do, one breakup only concerns the two people involved, unless something really bad prompted it, which has never happened to me directly.
It's because the (western?) default image of a break-up is a messy one. You don't just "remain friends". You fully cut ties and try not to even think of them until 4am.
You know, I think that's (the default, that is) only true in teens and tv. I think that I've seen and had a fair few breakups in my time, and more than 80% kept the same friend group and are absolutely on board with remaining friends.