it is in greater society so why not in dnd?
It is
common in greater society, but it is also incredibly bad there as well
It is bad and also bad actors exploit it, however.
Because the Calvinball nature of ruling not rules is also bad, IMO.
I disagree that it is bad, and have yet to hear a convincing argument that it is. I don't want a complex game with rules that cover every conceivable edge case. I know that there's a market for
that, there are games out there that cater to it, and they are not fully unpopular. But I am so, unbelievably glad that D&D no longer is that. IMO
I would recommend (re-)reading the MMI thread rather than re-hashing it here.
It seemed relevant to the conversation at hand.
You say this, but have you read this forum and how other DMs have cited the rules that its their game and that their authority is unquestionable? For everyone of those DMs here, there are at least ten more of them out there.
Of course there are bad, despotic DMs. But these are not some new phenomenon. It's not like Crawford wrote down the words "rulings not rules" and a thousand cruel and devious souls suddenly awakened from the mists of time to exact revenge on unsuspecting players. For as long as there's been D&D there's been DMs like that. Limiting the DM's abilities of arbitration isn't going to make those people go away, or change their ways at all. All it does is allow the game, and more specifically
the conversation, to flow more smoothly.
It's that conversation that paves the way for the greatest truth of all "rulings not rules" gives
players more agency too. The less a player is bound to the page, or their sheet, the more freedom they have to experiment, to try new things, to
contribute to the conversation of the game in ways they wouldn't be otherwise.