I love the idea of Primose53's Mum's knitted bedjacket, but honestly don't know when I'd wear one. I think most of us probably had one years ago, but personally I don't sit up in bed, I'm either up and about or lying down! When I was feeding my babies in the night I used to sit up in a rocking chair with a dressing gown or shawn round my shoulders.
Maybe if I had to stay in bed for some reason, bad leg or whatever, I might use one? But in that case my bedroom would hopefully be warm enough not to need it.
If I'm lolling about in another room I'd normally be fully dressed, if I was chilly I'd use a throw or a shawl.