You clearly don't fly very often. When in the US I've often flown west on one leg to fly east to my destination, because of hubs and focus cities that airlines base in.

This also covers why Delta (a US airline) wouldn't offer a direct flight from Santiago, you can look at the fifth freedom and see how hard and rare it is to be negotiated.

https://en.m.wikipedia.org/wiki/Freedoms_of_the_air

The only airlines likely to offer a direct route like that would be Chile's LATAM or Air New Zealand as routes like tht are a big trade issue.