Our original morphology put us in a situation where predators found us easy prey unless we banded together for protection. That same morphology also put us into a situation where protein was very difficult to obtain unless a number of members cooperated in hunting.
"Why don't cougars form such societies?
Why do zebra, horses, elk, and any of a number of other organisms form societies? Evolutionary paths are contingent on current state. The direction animals take in forming societies depends on environment, co-evolutionary organisms, current morphology, weather, and the luck of the draw.
Do slime molds form societies?
Tigers don't. Jaguars don't. Most cat species don't. Lions and feral housecats do. Lions are open-country animals whose best hunting strategy can be described as "stampede toward ambush." Why Felis domesticus does what it does is anybody's guess. I sure don't understand mine.