Maybe it's an evolutionary holdover from when Vulcans had more hair to protect themselves from the weather/climate?
(just taking a wild guess, considering that lots of terrestrial mammals have body hair, and both seh-lats
are extremely hairy)
I know Vulcan is a hot planet but didn't it get really cold at night?
All deserts get really cold at night.
Some deserts are cold during the day, too.