It's not "common". You have to deal with StopIteration only when you write an iterator with the low-level API, which is maybe once in the career time for most of developers.
The point is that the use of exceptions is built into the language, so, for example, if you write "for something in somegeneratorfunction():" then somegeneratorfunction will signal to the for loop that it is finished by raising this exception.
I’d say it’s more common for iterator-based loops to run to completion than to hit a `break` statement. The `StopIteration` exception is how the iterator signals that completion.
