"Allowing Kev to train the charisma skill felt like a mistake after a while, because once a character has gotten some basic charisma skill, every social interaction they do from then on makes them better at making people like them, which wasn't what I had in mind when I created him. That's what led to the story arc of Kev and Yvette. He'd accidentally become so charismatic that he convinced a rich old lady to leave her husband for him."
Most Sims players, however, don't set out to write sad fiction or just control one member of a relationship. They send their Sim out into the world, and it becomes successful and sociable and then comes love, marriage, maybe a baby carriage, plus a large amount of home renovation. At some point along this lifetime, however, you stop controlling just your Adam or Eve.
And that's where the roleplaying gets tricky.
Remember - The Sims is really about personality. It's about leading these dollhouse figures through their lives and responding to their needs and wants. But once you pick up a spouse and then beget children, the question of who is playing whom becomes complicated. All of a sudden, you aren't directing the life of a single personality, but of many.
This is quite different from party management in your standard fantasy or sci-fi RPG. In those games, the goals are clearly defined and each party member has overlapping ambitions, usually to kill the big bad at the end of the game. Yes, there are sidequests and occasionally some inter-party dynamics, but The Sims is an RPG that actually forces you to make tradeoffs. No desktop deity can be in two places at once.
Once your Sim gets married, you have now two characters to control and satisfy, but the days don't get any longer. Leave one of the Sims alone for a few seconds and they go off and do their own things. You queue up actions for both and try to keep everything balanced, but there is just enough chaos in the program for your Sims to tell their creator that they'd rather do something else.
Meanwhile, the player's mindset changes. Where you once identified with one character, one personality, one set of goals and aspirations, you now may find yourself identifying with both. You are roleplaying a family unit that cannot have all its needs satisfied immediately. Someone's lifetime achievement aspiration will take priority. The non-cooking member of the family might find him/herself in a job that requires cooking skill for advancement. Does the Sim family now deal with crappy and unsatisfying meals while the newbie chef levels up those long-neglected skills?
Children divide the attention even further. Just like in a real world family, the parents that you have been controlling have to set aside their own ambitions in order to provide for the kids. That great art and music room? Now it's a nursery. Sleep? Gone. Money spent on dates? Gone. The roleplaying of a single Sim with the world as his/her oyster is gone and replaced by ... something else.
At this point, who are you? Who does the player speak for or represent?