Imagine being in the passage seat of a car, having no proper electrical outlets to use. This comes in very handy, both in newer cars where an USB connection is available, aswell as older cars by simply attaching a cigarette lighter adapter with USB-A connections. Then you can play around with smaller synths while passing the time. You can also connect through AUX to get the sound through the sound system of the car, or if the other people in the car gets annoyed, just plug in your headphone!
Very recommended!