Comment by dguest

Exactly! They rely heuristics like that they are being served in a clean public restaurant which is presumably following health code, and is staffed by people who follow standard norms on hygiene. In some countries the norm is for the kitchen to be visible so the patrons can take a peak themselves.

If the restaurant has a foul smell and the food is served by a twitchy waiter who insists that the food totally free, I think most people will think twice.