Because some people enjoy being upset. They are never happier than when creating friction or expressing outrage. So they look for any excuse, and make the worst assumptions possible about the intent of others. These people are tedious to be around. I leave them alone to stew in their own poison.
Me? I assume that the server who calls me "Hon" is trying to be friendly. I like friendly. I'll assume that she is being friendly because making that assumption makes the dining experience more pleasant. I don't go into a restaurant looking for a chance to pitch a fit, I go there wanting to enjoy the meal.
Of course, these terms of endearment are the kind of informality that are more surprising to find in some places than others. I would not expect to be called "Dear" by a member of the wait staff in a $100 a plate restaurant with starched livery, but it would not surprise me in a café right off the freeway.
Here's an example of an occasion when a waitress used a term of endearment to good effect. I was heading west on I-80 from Salt Lake to the coast, and had stopped at a café in Winnemucca for dinner. Had a nice, light chicken something. The place was pretty quiet, so I asked the waitress about the road conditions, how far it was to Reno, what happened to the A&W, etc. She was friendly, in her 60's I'd guess, tall, thin, grey of hair and gravelly of voice. Empty dishes simply vanished, and my Diet Coke refilled itself as if by magic-- signs of attentive, unobtrusive service.
She asked if I would like anything for dessert. I thought for a second. She looked off towards the case where the pies were. "Our apple pie is awful good. We make it here." The case had a mirror at the top so you could see the tops of the pies. The apple pie did indeed look good. How did they get that crust?
She could see me weakening: "I could warm it up for you. Serve it with a big scoop of vanilla ice cream."
Me: "Gee, I don't know..."
Then she got ruthless: "I can smother it in whipped cream."
Me (reluctantly): "Oh, man. Maybe on the trip back..."
Her (mock serious): "Sweetheart, if you don't have yourself that piece of pie a la mode with whipped cream on top, you're going to hate yourself all the way to Reno. You know you will."
Of course she was right. I had the pie, the best apple pie I can remember having in my entire long life. I was happy all the way to Sacratomato. I tipped her extravagantly, and on subsequent visits to the café always hoped to find her, but she must have retired.
On the other hand, if she had been young, and called me "Gramps"...
...heck, I probably would still have had the pie!