Generally you don't use reference types until you encounter a need for something to be a reference type, such as being a reference to a particular resource, or

Generally you don't use reference types until you encounter a need for something to be a reference type, such as being a reference to a particular resource, or for usage compatibility with an external system. For example, there are something like eight classes exposed in the minimal swift standard library, representing concepts like managed buffers, singletons like the MainActor, and for implementing concepts like task-local values. These are all examples of types which do not lend themselves to being value types. Once you start getting to file and network I/O, or interfacing with Objective-C, you start to see the percentage of reference types climb.