It depends. Doctrine and rules of thumb are based on what experience has taught others and are generally a good point of departure for decision making in real time, however, if they become dogma they can get people killed. Every self defense situation is unique, and decisions should be made based on available info that is guided (but not ruled) by doctrine.
The other answers above describe some of the many variations of why/how it depends. All worth considering closely before defaulting to “go offensive”.