I always put a blanket down for them but that's only because they love snuggling in blankets. Especially Diva, she likes to make a little "nest". If they jump on the furniture before I put a blanket down I don't mind, but they usually sit and wait for me to grab a fleece blanket for them!
No, we have leather, and they don't mess that up, except the time Jewel decided to customize the corners of two of the back cushions, little stinker, luckily she has out grown that.
We have blankets designed just for th furniture and Amber likes to drag them around. I also found some really thick bathroom carpets we use just so we don't have drool spots. I find myself putting the covers over the furniture a few times a day. Amber loves to make her bed. We also have special blankets over the bed covers because both bullies have taken to sleeping with our daughter now that it is getting cooler. She has an electric blanket and they like the feel of that warm heat up underneath them.
I have small thin throw blankets that are on each end of my couch. I've always put something down, mainly because it helps keep it clean, well sorta clean that is. It's not so much a hair thing for me as it is a where they're paws have been when out in the yard walking and running through poop or urine and with 4 moving around the yard it's needed at my house.
For some reason Daisy has never shown an interest in getting on the furniture. She must be weird. Or maybe it's me because I am always on the floor with her? But I still have to wipe down the leather furniture because her hair gets everywhere anyway.