Haven't used hair dryers since the asbestos scare of the late 70s/early 80s, but like Kitt, we were educated (trained) to unplug any/all appliances whenever not in use. Many/most appliances come with a warning to unplug when not in use (for a variety of reasons), but many people don't read the literature, forget, or ignore because they consider it a PITA. (Not judging—these are the reasons.)
Nowadays,
GFIs/GFCIs (if you have them—depends on building codes & age of construction) reduce
some of the risk of electrocution. Still, unplugging is touted as a conservation tip, as many appliances draw power even when "off". Nevertheless, there are still good reasons to unplug when not in use (faulty components, frayed cords, pets, water mishaps, electrical surges...)—most importantly, the reasons we
don't think of.
We have some older (vintage) appliances that still function, and are in good condition, but we still unplug, cuz hey... you never know. Even new stuff can get
wonky.
CPSC Cautions Hair Dryer Owners
Doc