Situational awareness FIRST and always. Regardless of your carry method or holster, someone just MIGHT come along and konk you on the head and take it away from you. Somehow, that isn't something we hear much about however.
Location, surroundings, people... it all depends. And each person is responsible for their own choices and actions, as well as any consequences. I don't "MUST" do anything to suit anyone else. Your mileage may vary...