Lessee, people can't go partying like normal so get bikes and ride. More demand for bikes, both new and used, and manufacturing capacity is used up. Now people are riding and parts are wearing out. Parts don't magically appear out of thin air, they are manufactured; usually like the bikes themselves, in batches. Again, production capacity used up. So it's all a matter of increased use without a corresponding increase in manufacturing capacity. The real question is, why are some people surprised by this?