Yeah sitting on the edge of the bed is definitely not ideal.
I don't think I've ever actually sat on the couch to play games. As a kid I always sat on the floor, then I sat on the bed, then I moved to a desk, and I've been on a desk ever since. I played Destiny by sitting on the bed and that was a nice comfy experience.
If i had a couch in my room or a nice seat or something I'd definitely be more likely to hook up my PC to my TV every so often to play something. but right now moving to the bed isn't worth the effort of switching the cables around.