motiva
If you don’t practice, you may choke. Sure, this may happen anyway, but there is a higher possibility of you neutralizing a threat and coming out alive, if you practice.
I have seen people who were practicing for years choke when it came to cock the weapon and fire the thing. I have seen those who never got to draw. They went all “fight or flight”, and they couldn’t make a decision. In a gunfight, things happen in milliseconds. This may not be true if you are at a long range shootout, but at close proximity it is your training more than anything which keeps you alive.
It makes no difference if you are military, law enforcement, or civilian. Your chances of survival plummet if you are not properly trained. At close range, we are all equal, and it is our training and our instincts which guide us through the mess. You never know what shape you will be in, what situation you will find yourself managing, and 
what the surroundings will be. Day or night, cloudy, cold, raining?
If you make it a habit to practice, you increase your chances of handling the situation properly. If you don’t practice firing your gun; if you don’t develop a close relationship with your weapon of choice – and I don’t mean Full Metal Jacket, call it a girl’s name kind of close, I mean good knowledge of the weapon and its mode of operation – then you are at a disadvantage.
In close quarter situations, your gun is all you have. You usually have no barrier or cover. You need to make a decision, and fast. Once you make the decision to draw, you need to be ready to fire immediately. At least if you are a civilian. Cops warn people, civilians fire.