lusty sphinx
In short: There's this principle called symmetry in games. It describes how different parties have similar options to interact with the game state. Chess for example, is a highly symmetrical game. The only asymmetrical thing about is, is that one player goes first. Everything else is symmetric. The relation between the player and the computer in Super Mario on the other hand is highly asymmetrical, as the player has one character, while the computer has many. As well as things like traps, moving platforms, etc. And the options for interactions that Mario has vs. that of a Goomba or other creature are also rather asymmetrical.
To circle back to PnPs- You can have games that are pretty symmetric in terms of player and nonplayer characters. And many games do that. But just for arguments sake, imagine a game where the players play humans that are up against aliens which use biological equipment that is fused with their body. Like they don't take a knife with them, they get claws implanted. Which is represented by talents, as a claw would allow for a melee physical attack that deals cutting damage. We're at the very beginning, humans know next to nothing about the aliens and thus can't just loot equipment from enemy corpses. Now there's a good reason why I as a GM would want a talent tree for humans that my players can use and one for the NPCs that the players shouldn't even be able to see.
lost oar