The importance of ongoing user engagement in app development lies in its ability to drive retention and customer satisfaction. Continuously engaging users helps developers understand their needs and preferences, allowing for timely updates and feature enhancements. This feedback loop fosters a loyal user base, reducing churn rates and increasing lifetime value. Additionally, regular engagement through notifications, updates, and user-centric features can stimulate usage and encourage positive interactions with the app. Ultimately, sustaining user engagement is critical for the success and growth of any application in a competitive market landscape.