One of the reasons marketers use loyalty segmentation is

The high cost of finding new customers.

Explanation:

Loyalty segmentation is when customers are grouped based on how they interact with you product and services. It is aimed at identifying those that use a business's products and services frequently or that are loyal to the business.

Loyalty segmentation is preferred by marketers because it maximises the lifetime value of customers. It is expensive to get new customers, so marketers maintain already existing relationships.