Fluorescent lights have a variety of great advantages over old lighting technology, like incandescents. They're much more efficient, so they use less energy. They also have a longer lifespan—about 13x longer—so they don't need to be replaced as often
A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output.