It's possible that, if the ships are convinced that revealing themselves would lead to their own genocide, even Wolf 359 wouldn't bring them out of hiding. Remember, they aren't born (except for one very stupid instance where the Enterprise got knocked up by a space whatever, got pregnant and gave birth to... something,) they're manufactured by humans who could just as well shut them all down, study what makes them sentient and "correct" what humans might see as a bug.