Sooo Why cant unplayed sims make their own decisions (Marry,Children and Dating)

I use household management all the time to update and control the population of my town. This way, the core families have stayed around, and their genetics are being passed on. My third gen daughter is in a relationship with Bob Pancakes' grandson, actually. I've also added a few of my own sims too. I married some into families like the Goths and Landgraabs, and added a few other families to a couple of empty houses. The bonus to playing this way for me, is that I don't have to play the premades at all.