The reptilian brain makes sure that what we accomplished in evolution is preserved intact. These are the safe routes found over the years of one's life and safeguarded from generation to generation. Routines and rituals define and preserve lines of power and order. Most business activities and money transactions are reptilian. Efficient reptilian routines get the job done and increase productivity.
Automobile traffic is the reptile on wheels.
It is a very powerful, sometimes explosive, little brain. Territoriality arises from the reptilian brain and makes us touchy about our space. When our territories or routines are disturbed, we can strike out in irritation or violence. We curse at the car that cuts into our lane. We snarl at loved ones for silly reasons that are not at all silly to the reptilian brain.