The biggest factor of determining whether or not to try a head/neck shot is how accurately that person can shoot a their weapon. Also, shot distance, how the animal is standing, and whether or not the animal is moving determines if a head/neck shot is advisable. The heart/lung area allows a certain margin of error so that's why its so popular.
"No free man shall ever be debarred the use of arms. The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
-- Thomas Jefferson, 1 Thomas Jefferson Papers, 334