Why not?
I have been sleeping nude from age 7, why would I change now? I am nude from the second I am home until just before I have to go out the door. I have a few non-nudist friends that also sleep nude. Just more comfortable to be nude in bed and free from the twisting of the clothing one could wear. In the event I am visiting someone and have to sleep in something, I just wear a t-shirt and shorts until bed time and once in bed, remove it all and still sleep nude.
Why not indeed. I read many decades ago that sleeping naked is very healthy and allows your skin to breathe. After being covered up all day with clothes (for those of you still working) every inch of your skin needs to breathe at some point. So sleeping naked is the best way to keep your skin healthy. No brainer :)
That's exactly what Harry, Louis, and Niall of One Direction said too! It's good to know when young celebrities openly admit they sleep naked with no shame and for non-sexual reasons. :)
I can't even take a nap unless I'm naked. Something about getting rid of that last piece of clothing just instantly relaxes maybe. Perhaps it's all the negative reinforcement from when I have slept with clothes on (typically just underwear, country boys never wear pajamas) then wake up hot and fight the pull of underwear on my legs. Much more comfortable with nothing restricting my movement.