Because most people have so little experience with violence, they go into violent professions with no idea of what a “normal” response is. The keyboard warriors who teach that every potentially violent encounter is a life threatening situation and must be dealt with using maximum force and the clueless protesters who can’t imagine why any “unarmed child” would ever have to be shot, show the breathtaking range and depth of ignorance on this subject.
There are many ways to be stupid. Or, to put it slightly more gently, if ignorance of violence is a hole, there is a universe of fantasy possibilities to fill that hole-- fantasies ranging from visualizing world peace to nuke them all and let god sort them out.
But fantasies don't actually fill holes anymore than they stop bleeding.
So rookies have no idea of what normal is-- and there are many ways to be successful in violence professions. Most aren’t skilled martial artists, but some make that work. Some use size and strength, some don’t. Some rely on tools and weapons as a first option, some as a last resort. And there are a lot of ways to come to an understanding or a philosophy of force.
From Bruce Lee’s “Emotional content” to a sniper’s “The only thing you should feel is recoil.” There are completely incompatible concepts that work. Or “You must draw on your rage” to my “I don’t have the emotional energy to be angry all the time. Besides, when I’m angry I fight stupid.”
There may be a thousand stupid unworkable option for every good option, but there are a fair number of good options, too. And okay options. And passable options. And it's more global. It's not just a matter of what physical response is optimal in a specific situation (as if that answer would be the same for different sizes and personalities). At one level it's who you will be. Runners, Fighters and Talkers all successfully solve problems.
Again, this threshold rewires your brain. You can access your training, and it becomes less difficult the more experience you have.
And more, talking about modeling:
In the professional fields, rookies will model their mentors and cohorts. The first few encounters are very important to molding one’s fighting personality (See VAWG for more on that). If those first encounters happen in the company of mature, controlled professionals, the rookie will tend to become a good professional. If the rookie is working with hesitant and timid people, she will become hesitant and timid. If she works with aggressive people who use excessive force, she will become aggressive and uncontrolled. If she works with an individual or group that believes in only one option (e.g. talking, hand to hand, baton, gun…) she will be like the proverbial kid with a hammer seeing the world composed of nails.