Why
Because the manufacturers will do anything to claim your warranty is void ;)
I'm sure they are rated to operate fine in the conditions you find in bathrooms if installed properly and the bathroom is ventilated properly.
So if it's installed correctly it's ok?
@Howard started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
Why