As a SA, I call everyone 'darl' - it is a word I picked up from a girl I previously worked with and became a habit that I just couldn't stop. I was horrified by it at first and thought it was very small town of me to say that, but then I realised I AM in a small town and everyone calls each other 'darl' around here!
From SA's point of view, it is not really a term of endearment to anyone, it is just a way of saying a friendly hello, as in 'Hey darl, how you going today?' to people that you don't know their names. As soon as I find out someone's name, then I will always address them by their name and then try and remember something about them that they have told me in conversation, so that next time they come in I can ask them about their job, husband, holiday etc etc. I just think it's showing that you appreciate your customers and you want to give them a personal and welcoming experience when they are shopping in your store. Yes, some SA's may have other agendas and they've probably had their fill of rude, unappreciative customers that day and there may be a barb in there, but I would suggest for the majority of SA's, it would not be the case.
What gets right up my nose is when I say hello to a customer and I get grunted at - that is WAY ruder than being addressed as 'hon' or 'sweetie' to me.