The RAVPower is 50% smaller than a 13-inch MacBook Pro's AC adapter while providing the same wattage. Also, the RAVPower has two ports, a USB-C and a USB Type A so you can charge two devices at a time.

The RAVPower is also cheaper than buying a 2nd Apple AC adapter when you want to leave an adapter at your desk and have a 2nd one in your bag to use elsewhere.

What extra88 said. My Macbook charger is fixed at my desk and I wanted a travel charger that was compact and also had a USB-A port for other low-power devices I need to charge when I travel like my Fitbit and Kindle.