Unfortunately, this didnt make it into Sims 4, Along with many other things, MC Command Center allows you to have this sense of true story progression back! Normally, Sims dont progress at all, they just age and die. Just like real life! This goes for every Sim in your game, whether it be guy you see passing by in the park, or childhood friend you made years ago. They can go to college and get a degree, get marry, have kids, etc. This means that when sim move out of your active household, they still live their own separate lives. In Sims 3, all inactive Sims exist in the same open world.
If you have played previous Sims games, this term may sound familiar.