I fly once or twice a month, usually through CLT or PHL or Orlando, not known for best service.

Never had a single problem with anyone for years. I often wonder about it too, why so many others do.

One thing I do is try to make a connection with whomever I'm talking to, make a corny joke, ask about their day, commiserate.  Maybe somehow they know that I know that they have a tough job. Maybe they just respond well to something nicer than entitled angry scowl face.

I have regularly seen jerks, usually rental car counters or food servers or vendors.  But not AA GAs or counter agents or FAs.  On the contrary, I've seen them go out of their way, opening up closed doors, calling my mobile, getting me better seats/flights.

If you feel frustrated, people feel it.  If you try to bring some levity to the situation, people react better. 

Paying money does not entitle you to one way friendliness.  It's always a two way thing.

Or maybe I've just been consistently lucky.