The Sims had to dumb down the AI, because the autonomy algorithm for deciding what to do next in the absence of player input was based on dynamically scoring every possible interaction.

But if the characters always autonomously chose the best interaction, then almost anything the player told them to do would distract them from their perfect AI driven routine, and effectively make their lives less efficient and more miserable.

So instead of picking the top scoring action to do next, it fuzzed their behavior by picking randomly from the top several actions, making them less compulsive and more whimsical, and giving the player more opportunities to have a positive effect on their lives, instead of being a negative influence.

Then again, some people would prefer to play The Sims that way, by bringing them down like they're wearing a turtleneck and a backpack all day, messing up their otherwise perfectly balanced idealistic lives by acting as Satan instead of as God, more like Afterlife and Dungeon Keeper!