The topic of customer loyalty has gained significant importance in recent years, both in academic discussions and in practice. Companies can no longer afford to approach the market solely from a product-oriented perspective. Customers are well aware of their position and no longer accept mass marketing tools and impersonal communication. In this context, the question arises of how to best retain customers within the marketing mix, beyond just product price and quality. Many companies across various industries increasingly see the solution to this dilemma in the distribution of customer cards or the establishment of customer clubs. Implicitly, this reflects the desire to build a closer relationship with customers, to get to know them better, and to reduce anonymity.