But those 'gift' societies were hardly egalitarian paradises. In fact, they often made European feudal culture seem benign. Forced warrior class (which was the popular method of birth control), slavery and a large priest caste made it a great place for the chosen few. The rest of the community not so much.
Now, the biggest reason for that was, wait for it, limited resources. The Pacific Islanders often got into trouble overreaching their local environment. To solve those problems, they either started a war with a neighboring tribe or encouraged some folks to talk a long ride in a small canoe. Same with mainland tropical cultures. What appears to be a cornicopian paradise always has limits to growth. Always.
Now, until you get unlimited energy you will have these issues, robots or not.
All wars are resource wars.