There's improv theatre, which is fine, but a different thing. Infinite possibilities. But then we go and add numbers to games. We choose to give ourselves less than infinite possibilities, on purpose.
The ultimate reason for numbers and scores and tracked things like torch oil and number of spells and hit points and ability scores is to allow the players to feel desperation.
The purpose is that they feel how fucked they are in a minutely detailed way, with subtleties. A complexly textured desperation--unique to that situation. Against the wall and out of rope, against the door and out of strong people, against the giants and out of spells, against the grues and out of light, against the ghouls and out of clerics.
Too much crunch--too many things to track--and you can't see the fucked for the trees. You were attacked on a stat you didn't even know existed, you run out of something you didn't know you owned. You didn't get to feel desperation at all. This makes for an amazing chess game, or a typical first-go at Super Mario, but it's only fun if you immediately get to play again.
Too little crunch or description or time and you fall frozen without even seeing the mercury drop--you die and didn't even know things had gotten that serious. Full tank--empty tank.
Desperation is not the best emotion in games--triumph over desperation is. But it is the most necessary and useful--because without it you can't get to any of the best ones.
If you feel desperation, you can be sure of two things:
-You care about their character.
-You care about the outcome of the game.
If your GM's done all that, the rest is bonus points.