Any action can require a skill check to succeed, if the DM determines the outcome is uncertain. What you describe is one reasonable way to rule on various attempts to get NPCs to do what you want, but it is not the only valid way.
Exactly! Despite that I was just making fun of the debate, it is all a matter of personal interpretation. Because 5e (and D&D in general) puts most of the rules focused on combat up front, and then leaves everything else (i.e. skills, roleplaying, exploration, etc.) up to the individuals running the game.
Now, granted, there is an expectation that most rpgs, regardless of system, require some level of interpretation and allows for personal style and preferences. But there are games that do a much better job of using dice results to inform the narrative.
A d20 vs DC can only give you a binary "yes" or "no"/"pass" or "fail" option. Anything else is extrapolated without any ssolid guidelines or consistency between individuals or instances. A failure by 1 point is narratively and mechanically the same as a failure by 2, 3, 10, or 16 points.
This is why I love the mechanics of Genesys/Star Wars games. The dice results help to inform the narrative on many levels. You don't just succeed or fail on a roll. You achieve levels of success and failure, as well as mixed complications of advantage or threats.
Ex. You succeed at opening the lock, but activate the alarms. You miss the target and your weapon's battery cell fails. You convince the Hutt to forgive your failures by offering to perform at his party, and the Hutt is so excited about having a celebrity at his event that he decides to "keep" the character around as a permanent "employee". (That last one really happened in my campaign as a result of a negotiation check with mixed results: success + triumph + despair. That one roll inspired the entire next session in the campaign!)
If I were making a point here, it would be this: a lot of the debates and arguments in this thread seem to dance around the real problem, which is a lack of clear transparency and guidance in the rules or from the creators. This idea of "there is no wrong way to play" is great, until one person's way to play doesn't agree with someone else's way to play.
Which is why I find comments like "if I were playing at your table" a little silly. I can't imagine anyone ever wanting to play at a table ran by someone who had such a different and opposing perspective in the first place. And yet, people will feel attacked by the potential prospect of finding their way to play being challenged or threatened if they took a seat at a random table ran by random people.
Maybe that affects convention goers, or people who show up randomly and decide to start campaigns with other random people. I don't know. But in my experience, finding the people I want to play and have fun with is more important than just getting my game on. Yeah, I play less than I would like, and run fewer long-term games than others. But I prefer to enjoy those games that flourish with friends and players than quibble and bicker over obscure rules and varying interpretations. (And yes, I would be happy to sit at your table, if you would have me.

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