Perhaps your customers only interact with you intermittently. In between purchases, they are vulnerable to approaches by other suppliers. They may forget how great the services you gave them last time was.
You can put your name in front of them more often, between purchases, via a banded app that provides them with regular information. And it's a better way than an annoying tap-tap of advertising, if it's associated with useful information.
Not only will you maintain awareness, being the sponsor of useful information earns esteem for your brand. People will see that you have gone out of your way to give them value and they will respect that.