To be efficient in marketing spending, brands usually focus on their best customers first and then on their other customers. Typical objectives are to increase their customers' individual average transactions (IAT), spending and share of wallet. They often also want to increase customer loyalty. Less often, brands allocate marketing resources to communicating with potential customers, especially if one of their top objectives is to increase their base. Sales-driven organizations sometimes error on the side of bringing in new customers at the expense of constantly earning the loyalty of current customers, but this is an expensive proposition and one that is difficult to sustain in the long-run.
But I am increasingly witnessing this problem among brands. They know how to speak to their current customers well but they have not invested enough in understanding how to speak to non-customers. This is especially problematic if the non-customers are potential customers or if their current customer base is shrinking. These organizations become insular, only interacting with current customers and only understanding how current customers perceive them. Often, they only communicate through customer-specific channels and publications, failing to communicate or influence the brand narrative in other forums. Further, they do not invest in marketing research focused on non-customers who could become customers. Because of this, they really don't understand why those people have not become customers.
I have found that some of the deepest insights come from non-customers and former customers. If you understand how they perceive your brand you can better position your brand to retain current customers and attract new ones.
Don't make the mistake of understanding and communicating only with those who are closest to your brand. Don't become an organizational echo chamber. Much can be learned from understanding and communicating with those who are not part of your brand's family but who could be if you tried to better understand their concerns, needs and perceptions.