Because not every place is a shining example of liberal democracy like the United States.
Diplomacy requires representing your country, which sometimes requires advocating against the preferred policies of your negotiating partners. In some places, if you were subject to their laws, that would get you killed.
Diplomacy requires representing your country, which sometimes requires advocating against the preferred policies of your negotiating partners. In some places, if you were subject to their laws, that would get you killed.