It's not about garbage creation, is about reference cost. With ARC, you pay a penalty every time you pass a reference type, not only for memory churn. You can

It's not about garbage creation, is about reference cost. With ARC, you pay a penalty every time you pass a reference type, not only for memory churn. You can avoid this using value types, but this often results in a lot of unnecessary copying. It's not unavoidable, but Swift doesn't give good tools for avoiding ARC-based performance cliffs, so it takes a lot of profiling and effort compared to other languages.