The short answer is because we're tribal collective alpha/omega primates on which capricious evolution grafted a reasoning intelligent brain which functions best on an individual level.

The everlasting tension between these two things is the foundation of human history.

Had intelligence evolved from solitary primates like orangutans, our history might have been considerably different. Not better, necessarily. Just different.

Where does this leave humanity? A society where individual rights and freedom are primary drivers will always be the rare exception, like an ozone molecule wafting its way through a maze of catalysts. It's easy to create a totalitarian human society. It's kind of our ground state.

Freedom has to be fought for constantly. Not just physically, but intellectually.