I couldn't live in my house without a couch. I have crazy back problems, and sitting sucks/is painful for more than 10-15 min, so I spend a lot of time laying sideways or all the way down on the couch (I'm an athlete and train a ton, and don't just spend all day on the couch, I promise, but when it's time to rest, it's nice to be comfortable) I try not to spend tons of my time hanging in my bedroom, or else I find it really hard to get good sleep in there, so it's important to me to have a comfortable place when I want to rest. Also if I have more than 4-5 people over, it's nice to have a couple couches that everyone can fit on. I recently went over to a newer friends house and they had 3 big recliner chairs in their living room, and that was it....there were about 6 people over and some had to sit on the floor. I kept thinking if there was just a couch in addition, we'd all have a comfy place!
I should edit to add...I am a "comfy house" type of person. When I have friends over, they lay on the couch too...my house is warm and inviting and I'm not big on what the "style or design" is, and instead more focused on it being comfortable, welcoming, and a place I want to hang all the time. So that is just my personal preference, and why I really like having a big comfy couch!