>>12006239As others have said, it's a natural development of the brain. We are, after all, pattern recognition machines, and there is no point in our brains expending energy on recognising patterns we don't see in our daily lives.
As an example: I grew up in a predominantly white area (99%+) with very little exposure to other races outside of what I rarely saw on TV. In my late teens I moved to somewhere with a sizeable Asian minority population representing a wide variety of Asian ethnic groups, and for a while it was difficult for me because they really did arr rook the same. But over time I started to be able to discern differences until eventually they all started looking like individuals to me in the same way that whites do.
There is one exception to my learning process and that's mainland chinks. No matter how many of them I've seen and interacted with, the large majority of Han may as well be fucking clones of each other, both in terms of appearance and personality. Literal bug people.