As I collect world coins by type I have noticed that many 1950 to date coins of these areas are in very good shape. I have picked many unc or aunc coins from "20c / each" bins and wondered do they use coins there at all. Usually coins are very worn in poorer countries. One thing may be that coin types have been short lived and low valued after high inflation. Have you noticed the same and do you have a good explanation for that?
I've been in 9 South American countries and I found as many unc coins as coins with lower condition, so I guess you're lucky you keep finding the unc ones.
This is probably caused by what is described as chronic inflation, also named Latin inflation as it was commonplace in that region. Unlike Switzerland that has been using the same design for more than a century, in Latin America inflation eroded the value so quickly that sometimes coins became obsolete even in a few months.
