Hi, hon.
Seriously though, I'm 59 and I still get the terms of endearment from strangers in customer service situations like cashiers, receptionists, on the phone service agents,
and even nurses at doctors offices. I've been getting it all my life.
I think it might be because I have naturally light blonde hair. This comes with very pale skin (not dry, so not a lot of wrinkles), as well as light blue eyes, that are kind of round like babies' eyes. I also appear to have no eyebrows because of my light blonde hair doesn't show up very well on my pale skin. This all combines to give me a permanent look of mild surprise and helplessness. I now see that it may also include an unconscious perception of me as an awkward autistic person
Because of this, I came to terms with being called "hon" and "sweetie" a long time ago. I thought it would stop as I aged, but no luck there. The weird thing is that, because of my age and upbringing, I have accidentally started calling people "hon", too, especially if the addressee is younger than me. I don't mean to do it. It just comes out.
At this point, it seems like control of an interaction in this kind situation has developed into a mild struggle for having the upper hand. It has weirdly become like whichever of us uses the nickname first is the "grownup". I appear to my interlocutors to be either a competent, mature adult just needing some direction or a "slow", helpless person who needs special guidance. This is a hyperbolic description, of course, but I think my meaning is clear.
It can be hard to get to the other person see me as adult when you they have already decided I need guidance rather than direction. I usually just start reflecting back to them my understanding of what they have said, only using more sophisticated language. Sometimes the other person gets it and sometimes they don't. In the latter situation, I just go with the flow and behave like they have already perceived me to be. I have to be careful though. If my interlocutor discovers too late they have perceived me incorrectly, they get embarrassed, and things can get awkward.
This has been a long response to a simple question, but I just wanted to share my experience of this phenomenon.