because software development has become a professional enterprise, and with that people develop standards on how to interact with each other in large and small organisations, rather than just winging it in a garage.

Anyway, "we didn't need X then, why do we need X now" is an absolutely atrocious argument. Because demands and communities change obviously, and with them how we conduct and organise our communities and organisations.

Not having something isn't the same as not needing something.

"We didn't need X for Y years" is an excellent way of preventing progress, and/or gatekeeping. I feel like this has been covered pretty well online before, but I can expand my thoughts if you'd like.

A lot of sensitive people work in the field now, and they need a set of rules so other people won't be mean to them.

CoCs have been needed for 20 years and more. Now that we're getting them, there's discomfort at the disruption to the status quo, but it's a status quo that desperately needs disruption.