Primitivism is a complete rejection of historical materialism, that's why. Even more so than capitalist logic, which simply wishes to halt historical materialism with prolonging capitalism, primitivists want to completely reverse human development.
It's not feasible, not practical, and it's completely reactionary.
"As with the Christian religion, the worst advertisement for Socialism is its adherents." - George Orwell
Being a Humanist means trying to behave decently without expectation of rewards or punishment after you are dead. - Kurt Vonnegut
"I am confident that, in the end, common sense and justice will prevail. I'm an optimist, brought up on the belief that if you wait to the end of the story, you get to see the good people live happily ever after." - Cat Stevens