Its not at all important for me to say either to anyone, or for anyone to say it to me. I get annoyed when someone talks to me when I want to be ignored, I'm weird like that.
The only time I say it is when one of my male friends text it to me in the morning, which isn't quite often. He's the only one that says it to me, so I say/text it back to not be rude, but it's really not my thing.