When I was a kid, I thought knowing the rules to a game meant you knew the game. At some point, though, you realize that that isn’t true. That’s why there are books on playing chess. At most the first chapter, if any, of the book covers the rules.
A game’s rules are like axioms from which the game emerges.
Role-playing games are weird in that role-playing isn’t governed by rules. So, the things presented as “role-playing game rules” cover things other than role-playing. Which makes them easy to misunderstand.
Looking just at the rules, any role-playing game tends to look like it is about combat and one or two other things. They tend to look like anemic wargames. There’s been a lot of effort to create rule systems that cover more than just combat and magic, to create a “real role-playing game” instead of just “hack & slash”. (I certainly spent a lot of time on that effort myself.) For me, however, most of them seem to actually make the game feel more like a wargame.
Yet when I read stories of early role-playing game sessions, when I hear my friends talk about their sessions with the older games, when I think back to my sessions with the older games; there was an awful lot of role-playing going on. As I’ve said before, nearly all the stories I’ve heard about The Keep on the Borderlands focus more on things that happened in the Keep than things that happened in the Caves of Chaos.
Actually, though, I think there are some rules useful for governing role-playing. I hear gamers mention them a lot, but I don’t see them written in the rule books much.