> a simple rule "don't be an asshole" worked just fine.

Not a huge fan of overly broad CoCs, but they arose because, in fact, that simple rule did not work fine. It repeatedly did not work fine, in many groups engaged in many different endeavors. It worked not fine so badly and so frequently that people got tired of it and started writing out the explicit rules.

There's a lot of parallels between CoCs and sexual harassment rules. At first, it was a shitty free-for-all that was fun if you were part of the getting-away-with-it group but terrible for others. Then people said alright, had enough, we're going to make hard and fast rules against all this bullshit. Those first versions tended to be awful and heavy handed because they tried really hard to be comprehensive and serious about it, which is very well intended, but probably too far in the other direction. What we ended up with is probably vastly better, on average, for all involved. It's not as fun for people who enjoy treating others badly, but a whole lot nicer for everyone else.