Yes, in general, car guns are a bad idea.
But four days out of seven, I carry an LCP2 with no reload in my vicinity, so it’s nice knowing that there’s something nearby with a little more oomph to it. Is there a chance that my car could be broken into? Sure, I’ve had my car broken into, and I’ve learned from my mistakes. I had my truck broken into once because someone mistook my Bible in its leather cover for a purse, broke a window and ran off with that and a $40 leather jacket. I’ve lost camera gear due to truck break-ins, and every time it happened, I made the stupid mistake of leaving my gear out in plain view.
Unless it’s a riot situation where EVERYBODY’S car is getting trashed, crooks don’t break into random cars: They are looking for something, and when they see it, they balance the risk vs. reward and go for it.
No reward? Less risk. MUCH less risk.