In my Prima game guide for TS2, it actually spoke of how the main object of TS1 was dealing with the needs, careers, everyday life and keeping Sims happy. That was the main part of the game. There was also a different sort factor for them, like ranking which of the needs was top priority. In TS1, they just randomly selected between the top 3, which was hunger, social and bladder. Even if bladder was low, since it was a random choice, they may have picked going to the fridge instead, which is why, according to the guide there were so many bladder accidents and why it required much of player interaction. It also spoke of how Sims in TS2 had a much better "picking" system and that they can actually, for the most part, take care of themselves without much player interaction.