Story progression

Story Progression helps keep a town alive and balanced. With Story Progression uncontrolled Sims' lives progress normally. Neighbors may move away, new ones will move in, get promotions, have children, and even die. When you turn Story Progression off, your Sims lose the ability to "go steady" and propose marriage.

PROS
Sims grow older, letting you keep childhood friendships

Sims will sometimes have babies, allowing you to create new stories

Your sims will not grow older while others stay the same

CONS
Babies clog up the neighborhood.

When the game gets too many sims, they delete ANY uncontrolled family.

Your sims will switch jobs, even if its their Lifetime Want job.

Sims with jobs with branches will sometimes choose the wrong branch and lose their LTW.

Uncontrolled families never get LTP or complete their wishes, therefore if left unattended they ALWAYS get the Small Grave.

Uncontrolled children a bug where Child sims have Teenage bodies, planning clothes ages them into Teens, this has been fixed in the 1.3 Update.'

Babies sometimes come to single Sims of ANY gender, this has been fixed in the 1.3 update

Sometimes on ultra-rare occasions Uncontrolled sims die besides old age

If you dont get the "Name has passed on" notice (not from newpaper) you cannot find the gravestone as it's not in the Mausoleum