Carburetors have a fuel bowl that uses a float to regulate the fuel level. When you try to climb at a very steep angle, the fuel level gets out of control and the engine dies. Also, very rough roads will bounce the float causing the fuel level and consequently the mixture to change. Fuel injection also allows more radical cam timing (more HP) without rough idle, poor fuel economy, and less low RPM torque. Carbs cannot automatically adapt to altitude changes.
Like the man said, Carbs are a thing of the past.