They're great if you have to ride by yourself, because you're never alone. It's also life saving if an emergency occurs, to one of the group or an accident involving autos. The only requirement is a FCC license. Simple but necessary. Night riding is inherently dangerous due to low visibility.
Lights are essential both in front and behind.
White light up front, red light in the back. Also, reflective clothing and reflective tape all over the bike are extremely helpful. Try to avoid heavily traveled roads at night. Bicycle maintenance is key. Keep tires inflated, brakes working, bolts tightened, steering working, saddle secure, wheels trued.