I shall explain exactly why a bathroom lamp needs a cover.
Towels and splashes
if you happen to whip your towel around you, while drying your hair/body.. you just don't need it snagging on the exposed bulb
and IF you got a stray splash of water on a hot bulb it WILL pop and you WILL be showered with fine glass and it WILL be dark.. and you WILL step on it and you WILL bleed everywhere and you WILL trash the hall carpet hobbling to the next room.
Have I whipped a bulb with a towel while swinging the towel around myself? Yes...
have I stood on shatterd bulb glass..? yes
did I bleed a lot... tremendous amounts