Lighting in a building sets the ambience of the place. Like how restaurants place their lamps and lights so it might suit families or couples. And how clubs have different coloured neon lights in different areas so it will be flashy for club-goers. It also gives that whole sort of ‘feel’ to the building and makes it look more attractive, especially for bright lights on the outside of the building.
As such are examples of how lights can convey different settings and ambiences: