Personally I think it's both. Generally I'm not a story teller when I play the Sims. However I bought TS4 during the height of the pandemic last year. Through this time I've been virtually playing the same family, but they've created generations; cousins, aunties, uncles etc. In this sense (people may not agree) I feel like my game has sort of told it's own story with the way it's played out.
Obviously I've given them basic story lines with careers etc, but the game has sort of taken on a life of it's own if that makes any sense?