I guess I try to make the perfect house and have my sims live perfect lives that makes me want to avoid or at least severely limit "negative" traits that could possibly upset or compromise the work and time I put into playing the game. Managing a sim's needs can be enough of a hassle without them also failing at social interactions because they are loners, unflirty, noncommittal, or hate children. Maybe I should look into the fun aspects of "negative" traits more rather than avoid them because they could negatively impact my play-style.