I don't really go to conferences, and I've a full hat of privileges, so I don't know. Perhaps it is a mix of some bad experiences in the past, plus wanting to widen the appeal of the industry from its current straight-white-male preserve. I think it's using a code as a prevention mechanism, rather than experiencing an overwhelming number of incidents at every conference.
One of my philosophical musings is that I think people should do what works, but identifying what works - i.e. what will increase diversity and reduce harrassment in the long term - is rather tricky. One of the issues of CoCs is that they're sometimes regarded by a minority as left-wing devices, forcing a particular set of views onto people (identity politics, political correctness). This response is often a reactionary expression from people who, consciously or otherwise, would like to hang onto the privileges that have served them well thus far.
Thinking about the GamerGate and Reddit sagas, I very much admire the journalists who have been critically analysing female role models within video games, and I do not believe that misogyny and other forms of discrimination should be left unchallenged. However, I am not sure if someone has just moved a rock to see what crawls beneath, or given an anthill a jolly good kicking, and then been surprised at the result.
Thus, perhaps it is the case that moving too quickly in challenging stereotypes creates a counter-reaction that defeats the movement, though I realise that I am saying this with that full hat.