Professional pilots and ATCOs should know how to use microphones
unfortunately pilots/ATCOs don't come with innate knowledge of such things and it is no longer taught so unless it's pointed out to them they never know! Some refuse to believe even when it has been pointed out to them.
I'm grateful for people like Uplinker giving the occasional nudge on the basics
Another basic that pilots are sometime guilty of:- using a hand-mic in front of a loudspeaker. OUCH!