We value authenticity because it has a deep connection to the way humans use social connections to manage our vulnerability and to protect ourselves from things that threaten us. When we form connections, it is like all our respective vulnerabilities get entangled and tied together.
I think this encapsulates the human drive for authentically really well. Our emotions and depth of our connections is what makes us humans. While vulnerability strengthens relations, unauthentic behaviors and patterns can disregard it.