If you think about it Frito Pie is something put together with very cheap and ready ingredients. and I think it is a regional thing. In Texas and many parts of the west Frito pie is poor man's food. Fritos USED to be dirt cheap, and chili ingredients were cheap too.
Where I grew up and where I live now Frito Pie is almost unheard of. We have these instead
Navajo Tacos mmmmmmmmmmmmm
Invented by a Greek Hotel owner in Window Rock out of left over chili and fry bread.
The price on Fritos is ridiculous, especially with the smaller bags you now get.