Your customers will buy more using an application native on their phone. Certainly more than they will if they are using a website even if it is adaptive and optimised for mobile use. A mobile app provides an experience that is much more sophisticated and in tune with your customers needs than is possible using a website. The mobile app can be used when outside of data coverage. If a customer prefers not to use cellular data, they want to use WiFi only, then they can still have a great experience. They can continue to browse your products and even place orders ready to be sent when they return to a location with data coverage.