Sims 1 and 2 were theatre plays on a stage, Sims 3 and 4 want to be movies with full on illusion. Of the latter two, Sims 4 is targeted towards a casual audience, therefore I think one or both of these reasons apply:
- The devs think that when we try building our own worlds and they don't come out as good as we imagined them, or if we accidently cause routing failure or forget specific items, we will be disappointed, discard the game and don't buy dlc anymore. (I broke my police station's chief office once, but learned from it.)
- Players might create very detailed worlds that their computers cannot handle, resulting in them blaming the game and not buying dlc anymore.
