"Modulation used doesn't really change wave characteristics to such significant extent," True, except when the ionosphere is changing rapidly and phases change

"Modulation used doesn't really change wave characteristics to such significant extent," True, except when the ionosphere is changing rapidly and phases change across the bandwidth (as in fading). SSB helps and it's really great for narrow band comms but without the carrier the demodulated audio has pitch problems. Not an issue for basic comms but it is if audio has to be on frequency. SSB reduced carrier and synchronous detection is another solution.