No, nothing wrong with keeping naked, as long as you use them in an controlled environment..
People, pets, ect. can harm themselves and the tubes.
The tubes will probably run slightly cooler..
My BIL had a large St. Bernard who used to join us in my living room when watching a DVD, and large hound dog type dogs can drool sometimes, and with the shaking their heads for whatever reason, can sling substantial slobber wads in great arc`s across the room and I had visions of one of her "sling-nasty`s" landing on one or more of my 4 floor residing 275`s and popping one or more of the (16) KT88`s that would die like a trouble shooting/automobile repair lamp while working on a car underneath, with that one little drop of liquid that lands on the incandescent bulb !! Pow !! At nearly 63, I`ve seen it happen more than once, whilst helping friends work on the cars in low light..
So I keep my cages on, even after she passed on...
But who knows I might have a violent juicy sneeze and inadvertently shoot a expensive snot rocket into one or more of the amps eight feet, or so, in front of the listening seating distance..
Hey !! It could happen ?? HA !! I hope not !!
Folks can do as they feel comfortable with their wallet..
Kind regards, OKB