The interactions "goodbye" and "ask to leave" make sim leave the lot. However they do not always appear in the social menu. For what reason, I don't know. This can make it very difficult to get a sim to leave the lot. Sometimes they don't even leave, they end up just moving to a different part of the lot. Now I use MCCC to get the sim off of the lot but I do not want to have to rely on mods for a feature that should be working in the game.