Bill Zebub
“It’s probably Matt Mercer’s fault.”
This is the way I look at it.
5e has a skill that can be used to read someone, and ideally identify if they're telling the truth. If the GM calls for that skill to be used to make that determination, then I obey the result of that check, and whatever stakes are assigned for success or failure. My mandate as a player is always to play the system as it is presented to me. My personal opinions on its design are not relevant when I agree to sit down and play.
Let's start with a basic premise: the player says, "Can I tell if the NPC is lying?" and the GM says, "Let me have a Wisdom(Insight) check...". Some people feel that the player should have to abide by the result.
But let's run a thought experiment: suppose the player says, "Eh, never mind." Do they still have to roll?
Or, what if the player never asks? What if the player just listens to the GM and nods. The GM might say, "Do you believe him?" And the player says, "Not sure." Should the player be forced to roll, anyway, because the GM wants to know what the player (and the character) are thinking? That doesn't make any sense to me.
This is why I think rolls should only be called for in response to an action declaration that has consequences.
So I could see the player saying, "I'm going to keep asking questions and see if I can get the NPC to contradict themselves, so that I know if they are lying." And the GM might say, "Um, ok, but I'll need a roll, and if you fail you are going to piss them off..."
That being said, I think having skills on the skill list that are inherently passive and perceptive is a bad idea. I don't like both Insight and Perception being skills, and I'm not a fan of gating providing actionable information for the players behind checks.
Totally agree, for the above reasons.

