Many RPGs these days use a universal resolution system that covers all parts of the game. This was popularized with D&D 3rd edition and the "d20 System", the idea that no matter what you're doing in-game, you roll a d20, add modifiers, compare to a target number, and you succeed if you beat the number. I'm going to explain why this is bad (or, at least, shouldn't be used for every situation in every game).
This is distinguished from older games where you would have different rules to resolve the situation depending on what you were doing. Using AD&D 2E as an example (because it had a ton of these), you might make a Strength check by rolling 1d20 to roll under your Strength score. But if you were trying to perform a major feat of strength, you would instead of a percentage chance to Bend Bars/Lift Gates (the exact percent is determined by your Strength score). Or if you were trying to kick open a door, you'd roll your Open Doors score instead, with a different distinct target number if the door was magically sealed. Obviously, there's a lot going on here, and maybe we don't need three or four different subsystems just for doing strong things. But that doesn't mean that we shouldn't have subsystems at all.
The point of subsystems is to allow your gameplay to feel different when your character is doing different things or going through different experiences. It creates tactile feedback for the player that mirrors the kind of feedback the character would have. The value added is that feedback, the experience actually being different and not being the same gameplay with a new coat of paint.
Does it add friction? Yes, of course it does. Every mechanic adds friction in resolution. Sometimes that's the point of a mechanic - go read jay dragon's post about how rules are a cage. I don't necessarily agree that that's the point of every rule, but absolutely it is the point of some rules. Sometimes the point of a rule is to restrict the player, to add friction, to make it so that your whim as a player is not the only thing that affects the character and the shared imagined world.
The resolution of every rule creates an experience and, when done right, will reflect the experience of the character. This feedback helps ground the player in the game and should make it both more interesting and more real. If your experience as a player is identical whether you're in combat or fixing a wagon wheel, then the game is not accurately providing that feedback to you about the experience your character is having. If resolving the rules to fix a wagon wheel is a meditative experience, while combat is tense and frenetic, then we've got something much more interesting here than a smoothed-out universal resolution system that relies on the player to provide anything of value.
So to go back to our feats of strength, maybe you just use a normal roll for normal things. If you want to do something that would break a record, you'll need to do something more difficult. The friction involved in resolving the more difficult task - the pushback that the rules give you, when you try to resolve the action - that mirrors the pushback that the world gives the character when the character tries to take the action. In this way the rules serve to reinforce the roleplaying loop, by giving the player an experience that's analogous to the experience the character feels.
And certainly we don't want it to be exactly the same thing the character feels in a lot of situations (no one needs to get stabbed just because your character did), but if you feel something mildly unpleasant because your character is in an extremely unpleasant situation, that's working as intended. If resolving the rules to determine whether or not your party member dies after their severe injuries causes you to feel stress and tension, that's a good thing.
And if a negotiation with the king feels exactly like a relaxing day fishing which feels exactly like combat? Something is being lost, there, and subsystems are how we get it back.