Much of the matter comes down to where people come from; the materials to make sweets don't exist worldwide, and if a group of people are unexposed to sugar, over a long period of time, before it's introduced, then both culturally and genetically they have fewer reasons to take to it.
There really is an NPR spot on this: https://www.npr.org/sections/thesalt/2015/07/24/425609156/the-g
[So, tradition and sensitivity, essentially.]