@eniko we do sleep in the same bed, but we bought a king size one a while back and I couldn't go back down size.
Also I understand that it is not uncommon to sleep in separate bed, room or both. I know 2 close friends couple where it is the case (for various reasons)

@eniko also, on king size, you have the possibility of having two separate blankets which is way better than it seems at first.
I know some Asian countries don't really have king size and instead use two side by side double beds which can allow for different mattress and bedding set