In my opinion this is completely backwards. You should reserve all of the rights you intend to exercise. This is indeed what most companies have always done; you don't go randomly giving people copyright licenses to e.g. your characters and then get mad when they use them. Instead you just tacitly allow some unlicensed usage of your IP. That really is a social contract that exists in different places across the world.
I understand that some people didn't always understand the consequences of their choices, or maybe wrongly thought we all agreed on these unwritten social contracts, but we don't agree at all and I hope the lesson is learned well.
None of my prior work contracts stipulated not to microwave fish in the break room, or how often I ought to shower; yet "Don't stink up the office" is rule most folk innately know, recognize and respect as part of being a decent colleague. Some rules have to stay unwritten (or be in vague clauses), otherwise every contract will be tens of thousands of pages long.
Look, you can argue about the existence of social norms till the cows come home, it won't change the fact that there is a non-trivial subset of open source developers and users that believe the lack of discrimination of any kind is exactly the point of Open Source. The definition is not stipulating these rights indiscriminately by accident, and it did not have to be written that way. I will acknowledge that some people in the community clearly believe that enforcing unwritten social rules with regards to Open Source is the best practice, but I don't accept that this is the common or obvious viewpoint. I think that viewpoint is overrepresented in spaces like Hacker News with a lot of startup-adjacent folks but even here I wouldn't expect the majority of people to agree with this.
P.S.: This all having been said, while I think that there aren't commonly-shared unwritten rules w.r.t. who may do what with open source software pertaining to its copyright license(s), I don't think there's absolutely no "unwritten rules" in open source. For example, I think the CLA rug-pull pattern is a pretty dirty trick, but that has little to do with open source licenses and more to do with outright deceiving people. And even then, it does beg the question of why you would agree to sign something that explicitly grants that right when there is absolutely no reason to do so.
I understand that some people didn't always understand the consequences of their choices, or maybe wrongly thought we all agreed on these unwritten social contracts, but we don't agree at all and I hope the lesson is learned well.