On Apple’s platforms the primary motivator for sharing code within an application is that an application isn’t just one component. You may have an application t

On Apple’s platforms the primary motivator for sharing code within an application is that an application isn’t just one component. You may have an application that has any number of app extensions in it that provide access to its features in various settings; if you build that functionality into a framework and use it from the app itself and any app extensions, it’ll still only be loaded into memory once even though there might be several processes mapping it. Creating frameworks and libraries also helps the developer break down software into more testable components, which doesn’t necessarily require them to be dynamic but if you do go that route you remove an axis of variance that can result in different behavior. For example, a static library on UNIX is just an indexed archive of object files, so it doesn’t have a single overall set of imports and exports or a single set of initializers to run at load, whereas a dynamic library is a fully-linked module with its own set of dependencies, imports, exports, and initializers. If you assume equivalence between them you’re eventually going to be wrong, often in hard-to-diagnose ways.