We can't. We live in a studio flat and it's a room, a kitchen and a bathroom.
I had this issue recently where I was so pissed off that I considered ripping the spare mattress off the bed and sleeping on the floor. I considered the relationship to be over at that point, but when the arguments gets so bad that I want to end it, she has an ability to sweep things under the rug and move things on.
I've slept on both couches and mattresses on the floor before, before her, due to reasons unrelated to women. No matter how nice a couch is, it doesn't compare to a mattress, though I'm quite tall.
If we did have a spare room or a couch, I'd only sleep on it if I was angry. If she even tried to "punish" me in this way, I'd refuse, be offended, and give her the marching orders.