The staff I just encountered were two young men who clearly don't want to be there. They were efficient in swiftly taking care of me, but inefficient in smiling. The young girl before me was apologizing to them for not be sure of her order and they didn't so much as say "it's ok" or smile or anything....just blah...I think the girl felt bad because they were so dang serious and possibly intimidating, but I don't know...just a passive observation.
Just smile. It's not hard. Really.
That is all.