What makes coupons very powerful is that you can add new coupons at any time and they will automatically appear on the application. So you can use this function to get your customers coming back to your shop, restaurant or what ever business you have.
Even more powerful is when you combine the Coupons with Push-Notifications. Imagine you just added a new coupon in the app. Then you can send out a Push-Notification to all of your customers and let them know that there are a new coupon they can use. That if Free marketing that will get your customers coming back more often.