In order to understand this, you must take into account several factors. The culture and societal aspects of North America, and other westernized countries tends to shun open breastfeeding; mainly because of ideas of nudity. It's not forbidden and you are still allowed to do it, but these norms have stayed anyways. This would not be the same in, say more impoverished areas, where it is more socially and culturally acceptable. Also just because people don't breast feed doesn't mean that they aren't giving their baby breast milk in a bottle.
In regards to my last sentence, sometimes it can get painful when a young one chomps down. This is why some mother's just defer to using a bottle instead.