Mirrors are highly reflective surfaces where light can easily bounce off. Same goes for pristine bathroom fixtures like ceramics, tiles and glass. Hence, bathroom and mirror lighting is not only about the aesthetics of the fixture (whether it will blend well with the design scheme of the room) but it is strategic as well, ensuring that light does not bounce off reflective surfaces which causes glare and bad lighting.
Often, bathroom mirror lights are hanging or overhead lights so that the light beams will be cast downwards just across the surface of the mirror but not directly towards it. LED bulbs are also popular among mirror lights as they can be enclosed within acrylic casings so that water may not damage them.