A bit of formality as a sign of respect, to make for respectful conversation. The difference, for those who speak other languages, between the familiar and the formal. An acknowledgement of lack of familiarity, some framing of social distance, and formal respect.
I had a boyhood friend who headed a SORT team. His name was also Robert. We often referred to each other in public as "Robert" with an eye to us both having the same name and maintaining some measure of formality in social situations.
And yeah, my late wife taught cultural anthropology, which discusses how one refers to others and its variances depending on social situations. Singer, assuming he did travel extensively, would know quite a bit about this stuff.