This flies in the face of my own experience travelling all over the world, where the poorest people would offer me extreme generosity and not accept anything in return.

Maybe it's bias because I'm an "exotic" white guy in many areas and not just a random down on their luck average guy from their own region.

I've also been offered generosity by rich people, as well, but, I will generalize, that mainly came after I demonstrated some proof that I didn't actually need their generosity

Maybe it's country dependent. I have seen what you describe in countries where christianity is the dominant religion and most people in those countries something like 70 to 80 percent identify with it. And religion in those places is most prevalent among the poor, so much so there is a direct relationship between poverty and religion, the more religious, the poorer.