...which is also the most likely reason for a memory leak when you manage your memory through refcounting (or rather: with refcounting, memory leaks are just as unlikely as with a GC).
But even without both, these days (with memory debuggers and profilers integrated into IDEs) pretty much all memory related problems are 'trivially debuggable', this stuff isn't as scary anymore as it was 20 years ago (e.g. Xcode's Instruments has a leak detector which lets you click on the line of code which caused a memory leak, and Visual Studio has similar features).
Memory leaks have never been scary in tracing GCs and they are not too scary in RC as well, though I would guess that cyclic references leaking is definitely a top 10 bug for swift and alia. Memory corruption has been/is the real issue.
But even without both, these days (with memory debuggers and profilers integrated into IDEs) pretty much all memory related problems are 'trivially debuggable', this stuff isn't as scary anymore as it was 20 years ago (e.g. Xcode's Instruments has a leak detector which lets you click on the line of code which caused a memory leak, and Visual Studio has similar features).