Scott Young recently profiled Ben Franklin and Van Gogh as people who used copying to learn writing and painting, respectively.
He points out that by devaluing copying in creative achievement, we also throw out its value in learning fundamental techniques.
I've seen this in action watching so many people improve their programming skills at the Recurse Center. Copying existing paradigms and software is an speedy way to quickly and thoroughly understand new architectures and techniques.
For instance, building a to-do list app can be your first mobile app. Cloning Requests teaches you about structuring an API. When I attended, I'd heard that Python was bad at concurrency, so I built a deeply unreliable chat client to probe exactly how it breaks. It was ugly!
None of these are Original Ideas—chat apps have been around for decades—but all are incredible learning experiences. This was a great reminder to keep this learning tool in my back pocket.