It's friendliness.
Do they go out and hand-select the nicest people they can find? Or is there some sort of super-courtesy basic training boot camp? I'm just going to assume it's the boot camp. I am envisioning CFA troops in their black fatigues on an uphill march all saying things like "oh excuse me, sir" and "after you".
It might behoove me to just hang out in a Chick-Fil-A for a full day sometime, so that maybe some of that amiability will rub off on me, and I will be much less of a jerkface.