That is the nature of roleplay and social play. Anything that can't be measured by ones and zeroes, like player's ability to change plot or interaction with characters, relies on DM, and in CRPG, content is DM. Even things that are at border between combat and roleplay, like Stealth, rely on content. Or will you be satisfied with linear corridor with Thief stealth-system, as long as it counts sound/weight/has shiny stealth-gem?
Say CHA adds #of companions, but then it's useless for solo combat char, what will you do - make it add even moar dmg to solo char?
How far can one go sacrificing everything to the altar of combat until whatever particular parts of system used to represent lose their meaning whatsoever?
Roshan is right, meaningful consequences for actions are a more natural way to make players roleplay and concider their actions. Players murder NPCs either if they are chronical powergamers, or, generally, when they already finished the game and want to test limits of the game. That is why when playing Obsi games in particular I, for example, am always conciderate in my actions in the world and try not to murder everything on sight - I know that there is possibility of losing additional content that way. That and me not being dumbfuck dorito douchebag (CHARISMA LOL USELESS DUMP THAT) and actually caring for characters, their fates and plot and shit.