A lot of times bathrooms lack the proper amount of lighting, as well. It's just too dark and there may not be a window.
Another thing to consider is light placement. When you stand in front of the window, light hits every part of your face. With a bathroom light, the light comes down from above your head and casts shadows on your face. The best artificial lighting design incorporates lights on the top and the sides of the mirror, not on the top only.