Being nice only to the people who can upgrade your order isn’t kindness. It’s customer strategy.

Charm aimed at a counter is a tactic, and the people behind it recognise the species immediately. The giveaway is that it switches off the second the transaction ends. Nothing is wrong with being pleasant to someone who can help you; the problem is when that is the whole set of people you are pleasant to.

Be exactly as warm to the person who has nothing to give you: the one cleaning, the one who cannot change the policy, the one you will never see again. Keep it brief and real rather than performed. The habit also makes the whole day less tiring.