It does but a Carrier wave is useful as a last resort.
It can travel a long ways, everyone cam pick it up, and would allow for even the most catastrophic of events to not stop communication
Carrier wave transmissions are dependent on the teaching of Morse code and active monitoring of old radio frequencies, neither of which exists in the modern world. Indeed, one of the biggest practical advantages of GMDSS is that it enabled slamming the door on this wasteful, old-fashioned BS.