A CMK is crucial for several reasons: - Centralized Data Management: Ensures all customer data is stored in one location, making it easier to manage and update. - Personalization: Enables more accurate segmentation and targeting, allowing for personalized email content. - Customer Journey Mapping: Helps in tracking the customer journey, making it easier to identify touchpoints and optimize the customer experience. - Data Security: Enhances data security by using a single key to encrypt and decrypt customer information.