The main purpose of a mobile app development framework is to provide developers with a comprehensive set of tools, libraries, and best practices for building applications for mobile devices. These frameworks streamline the development process by offering pre-built components, user interface templates, and APIs that simplify the integration of features. They help ensure cross-platform compatibility, allowing apps to operate on both iOS and Android devices. By utilizing a mobile app development framework, developers can reduce development time, cut costs, and enhance overall app performance and user experience, leading to more successful mobile applications.