Also, price varies among countries - and in this digital age it should not. I wonder who will be the first to say something along the lines of "It's not happening to me, so it doesn't matter."
In the UK, a Stuff Pack costs £9.99. And a Kit Pack costs £4.99. Kits consist of new skins and clutter. Clothes... well, they look nice, but there's only so much a Sim can wear at once. And we do have SO much good CAS as it is.
Stuff Packs generally had a new functional item in them with new actions, sometimes new traits or even a new job. Tiny Living had a new way of building. Paranormal Stuff had a new job that tied into Occults. Laundry Day had laundry. Nifty Knitting had the ability to knit things for money and to wear.
Stuff Packs are overpriced as it is, but compared to Kit packs...