The Term RPG starts off as a form of Board Game, in which players will assume a character of their own creation entirely and interact with other players to made up a game and story.

When the early adopters tried to migrate these into video games, they face difficulties with the limitations on what video game is capable of at that times, hence the mechanism was tweaked to maintain what they can do and remove what they can't do. Trust me even now some developer still admit they are still trying to adopt the true RPG expierience into video games.