Answer:
Consumer behavior changes organically and has changed a lot in the past years, tending from cars to public transportation and, in some cases, bikes. That is due to increased traffic, maintenance costs, new services (such as uber), etc. There is a social link between bikes and crime, where motorbikes could be associated with socially less desired elements. Finally, one of the factors is the marketing innovation and development; the motorcycle industry is based on either a classic and conservative marketing, such as Harley Davidson or a futuristic and technological one, such as Toyota. They find it hard to change their marketing fast enough to respond to consumer behavior changes.
