To be fair, from what we see hunter gatherers also made continual "war" on each other through raiding and battles. North American tribes on the whole had a mix of trading and ritualized warfare for centuries before Europeans were involved. And they burned often huge tracts of forest to manage grazing lands. And overhunted and overfished and then moved on to new areas.

Its just that population densities were on the whole lower. And there was a lot of land and resources to live from. So the impact was lessened.

But even then, there were in fact tribal groupings that effectively wiped out other tribal groupings.

Also it's becoming clearer and clearer that the line between settled agrarian and hunter gatherer was a lot less clear than we initially imagined. There were all sorts of grain and maize growing societies that continued to rely on deer and fish for their protein sources and trade in skins etc for hundreds of years after they started tending crops.