Do you give your sims back stories?

All the time! I also give EA-made households that come with a new pack a more fleshed out background like a few family secrets and perhaps a couple distant relatives that I create just for taking some pics for the photo wall, and then might delete as I don't intend to play them. It's also more fun seeing a not played sim walk by if I know their background.

All the time. It's funny how easy and simple it is to come up with a story especially when you create Sims. In Willow Creek when I first got the Sims 4 on PS4 I made a single girl she was a Science girl. So I made her an astronaut. She met and fell in love with an NPC who ended up working in the Criminal Career he is a Matrix kind of guy. They had two kids. Both kids ended up being gay (randomly chosen with my app I have) and it just kind of goes from there.

It's awesome to me how the story just flows and unfolds and then I create new Sims and it starts all over again.

I started with 1, then. I had 4 more families and they became my founding families and I started creating a legacy game.

Now I'm in the 2nd generation and starting to see the 3rd generation pop up. So I can definitely say I give them backstories and stories. ^_^

Yes, back stories are a necessity. Playing The Sims 2 I used to use the Storybook to keep track of what I'd done with their lives ?

Yes! This is how I always play.

Always! For me The Sims is all about telling stories. I tend to create my characters first and plan their personality, backstory etc. in depth before I bring them to 'life' in The Sims.

Oh, definitely. Even with the premades, I have certain...head-canons. For instance, Angela and Lilith were teenage movie stars, hence the Pleasant fortune despite their parents' lackluster careers in The Sims 2. Lilith has a strong interest in mechanical things. Brandi Broke (TS2) is Mortimer Goth''s love-child. The Landgraabs are imposters, as the real Malcolm Landgraab is a custom sim I make modeled after his appearance in SimCity 3000.

I don't give my Sims a background story. The premades I play already have a desciption, and any Sims I create myself start their story when I start playing them.

Always. I can’t get invested in sims without backstories.

Definitely. Usually the back stories are just in my head but I find sometimes when I create a family it inspires me to write stories/ comedy scenes involving the characters.
The family I have used the most for this is a quartet of former warlocks (created before Realm of Magic came out); two twin brothers who end up sharing a house with two twin sisters. All have come to the human world for different purposes: Norrell is bored with the stuffy life of being a prince (plus humans are more fun to prank); Tadeo isn't really into magic and wants to be a writer; Rhydia loves exploring new places and wants to help people; Leoni wants to make it big on the comedy circuit.
(I'm unfortunately not able to post pictures at the moment but the Sims described above are the four who are in my profile pic).

I do miss the section in Sims 2 where you could write a bit of individual bio/ backstory for the characters.