The number one reason that I don’t just sit in a car, in today’s world...
Situational awareness, and watch those who even look at you, or leave.
Over the years I have read a lot of news stories that include people being shot while sitting in cars. Enough to make me realize the danger of this.
Plus it makes carjacking much easier. At least if the car is moving most of the time it is harder for someone to force his way in.