> We've been working fine like that, both online and in the real world without any CoC
I'm not sure what you consider "fine". Misogyny has been par for the course for a long time. Not to mention verbal degradation of e.g. ethnicity, gender, and sexuality. We have not suddenly removed these formerly accepted behaviors, even though things have gotten better.
It is possible that there really isn't a problem in communities you engage with, and that consequently their CoCs make little positive impact. But do you really know what kinds of inappropriate remarks e.g. women around you face? It is easy to dismiss anyone who had such negative experiences as a professional victim, but surely the world doesn't just consist of "perfectly reasonable and encompassing people that know better than to offend", "harassers that purposely ignore any community guidelines"?
In short: Yes, CoC creation and enforcement will naturally appeal to certain groups of people that have more personal motives than those of the community. The same is true of HOA, police, unions, workers' councils and so on. But please be careful to dismiss their usefulness due to this.