† The Royal Society of Chemistry says this — "The oil, being liquid, fills in the valleys and caves of the pan surface and when it gets hot it reacts with the metal atoms of the pan and forms a coating called a patina. This leaves few free metal atoms to react with the food. This coating can easily be removed by detergents, however, so it has to be reapplied before each use of the pan."
Things I need to dig into and confirm:
Some deeper reading about the chemistry of how food sticks and doesn't stick: