I suggest you check out the details of what the mod does. It's HUGE in scope (which is why it's so much fun).
Here's the FAQ for it.The game's story progression doesn't do much, and at a certain point started doing even less. Townies won't get married, have babies, change careers, get promotions, get divorced, or do anything else. At this point the game simply swaps families in and out of town depending on demographic needs and that's about it.
Nraas story progression gives the families in town lives similar to your playable sims. They can advance in their careers or even change them based on their traits and lifetime wishes. They can learn skills. They can fall in and out of love, get married, have affairs, have babies, get divorced, etc. And depending on how you set it up you can be informed on all of the town's goings on if you wish, which makes the town feel really alive.
