These sell the for same reasons a treadmill sells. Convenience. Everyone says to just play, but that is not easy if you work long hours. Can't play a bass while you are on phone at work. So not completely useless. Or if you have a long commute, this could combat boredom some. These really aren't a primary tool, but an aid, to use during times you are doing other things. It just isn't always practical to have a full size bass within arm reach all the time.