As for me, I've grown up in a military family as well as 10 years in martial arts. I say sir/ma'am as a sign of respect. Now when I call a passenger by their name it's usually when I'm having to screen a selectee and I have the boarding pass in my hand and the passenger comes through and I pronounce their last name(sometimes the first, depending if I can pronounce the last name) to Identify the person.