Comment by retsibsi

They're doing the job for the money. They're relating to the customer both as part of their job, and as an actual human interaction. (Obviously the extent to which this is true varies a lot depending on the individuals involved and the context.) Believe it or not, sometimes people are genuinely friendly, even at work, and even when they're not receiving any extra compensation for going beyond the required level of politeness. Those interactions are, IMO, worth more than forced "friendliness" from someone who is simply looking to get as much money as they can out of me.