I am fully prepared to get flamed for this post.
I "carry" a pistol in my car. I carried a Colt Government Pocketlite .380 for a few years before retiring it; presently I am carrying a Kel-Tec PF9. Sometimes I put it in a pants pocket or jacket pocket when I leave the car, but it is illegal for me to carry it many of the places I go (such as courthouses) so it often stays in the car.
I have a two-year-old daughter. She gets into things and she is often in my car. You can see where this is going, but that is just one example. There is a 0% chance of an accidental discharge with an unchambered semiautomatic pistol. There is somewhat greater than a 0% chance that I have the second or so to rack the slide and load a bullet if I need to. While it may be less than the best protection possible should the unexpected arise, it's better than no gun and it's the most I'm prepared to do at this point in my life.