To pick one of my own: defamation is something that is determined based on your actions and the state at the moment they happen. If I say something potentially defamatory about you, it’s judged based on what I knew at the time, what I said, and how it would be understood by a reasonable person at that time.
You can’t rock up later and say “well looking back at this thing you said 10 years ago, we now know it was false” or that a reasonable person today would think differently about it.
By contrast, if we made a rule saying that culturally significant games are due some set of societal protections, a game dev has no way to know if their game would meet that threshold when they release the game.