Exceptions are useful when something has gone wrong that's outside the immediate scope of the problem. They should almost never be caught close to where thrown, since if they can be satisfactorily handled there they can be satisfactorily handled without throwing anything.
One example is C++'s containers, which can throw bad_alloc if they can't get the memory they need. The people who wrote the container have no idea what should happen if the container can't get memory. Perhaps this is an expected thing, and the calling code has alternatives. Perhaps this is recoverable. Perhaps this is fatal, but how should it be logged?
Yes, it's possible to pass back error codes, but will they be used? I see lots of C memory allocations without tests for NULL, and printfs that just discard the return value. Moreover, lots of functions don't have a distinguishable error code, like negative for printf and NULL for memory allocation. Where any return value can be valid, it's necessary to find a way to return an error indication, and that leads to more complication than most programmers are willing to deal with. An exception cannot be ignored, and doesn't require lots of defensive code.
