People interact even when they are sleeping. My Man and I often touch, fondle, hug, rub and even start making love while sleeping. I can't sleep without him. Bed sharing helps with bonding and I think it strengthens a relationship.
We don't always "plan" sex, but often just having our bodies up against each other while sleeping is enough to get us starting. I know we have more sex than if we slept separately.
My Man's parents slept separately, and there was no.... warmth or spark between them. I don't know which came first, the death of their passion or the separate beds, but I'm sure sleeping separately didn't help the situation. He always said he and I would never end up like that. We will always sleep together, as long as it is physically possible. I'd prefer to actually be one of those couple who die within minutes of each other, asleep in their bed.