When you’re traveling, it’s easy to see the origins of modern tipping. A tipped service in a foreign land is typically performed by someone who is not an employee of an establishment but works either as an adjunct or as a free agent  — a shoeshine boy, for instance. In a “third-world” city, a self-styled tour guide might be tipped in return for leading a group of sightseers. In Italy, a Neapolitan street urchin might offer to protect a parked car in return for a gratuity.

In both cases, the inference is clear: if you don’t employ me, I will hurt you. This thinly veiled extortion is the subtext to much tipping: if the propertied individual doesn’t comply with the demands of the semi-employed, something terrible might happen to them or their things. So tipping began essentially as a way to stave off violence by the indigent, forgotten people; it is a social contract adhered to by the privileged class who fear and disdain the less fortunate and are aware of the failure of their own class to create equity.