Each to their own. I sleep on my side so that’s all the space I’d need to rest and read or watch something on my phone for a while then sleep for the rest of the trip. I’d rather sleep through flights than sit uncomfortably crammed into the pathetically small chairs they give you these days.
Beds in Asia often don’t have a lot of padding, they aren’t designed for side sleepers, you would be on your back quickly. Incidentally, a wooden chinese bed will cure you of side sleeping in a few days if you ever want to go that route. I found my sleep was better, but I reverted back to side sleeping quickly after getting to use a normal western bed again (after about six months of using the Chinese bed).