While belt drives on a motorcycle require less maintenance and are smoother, they are not as efficient as chain drives. Consequently, chain drives are more popular.
A belt drive requires less maintenance, lasts longer and is cleaner. It also delivers a smoother ride, which is why this type of drive system is most commonly used on cruiser motorcycles.
A chain drive, on the other hand, delivers power more economically than a belt drive, and it sends more of the power that the engine produces to the wheel. While they require more maintenance, the improved performance means they are the more common type of drive method.