Well depending on what is broadcast, it might have a regular structure and perhaps there's some reason you'd want to randomize the broadcast signal. Maybe some

Well depending on what is broadcast, it might have a regular structure and perhaps there's some reason you'd want to randomize the broadcast signal. Maybe some highly specific noise in the environment that happens to resonate with the signal structure? Alternatively there might be protocols which have mandatory encryption as part of their specification. Or you might be using a combined encryption-authentication mode, but only for the purpose of authentication on ham radio. Those are all a bit of a stretch though.