That is what a reasonable person would do, but unfortunately there are too many people who just want any excuse to smash someone’s window and hope to be called a hero for it. My car has rain guards for cracking windows, remote start to run with doors locked, good climate control, etc. I know my dog would be safe and comfortable for a bit inside of it, but I don’t trust self-styled “good samaritans” or straight-up dog thiefs to not smash up my car and steal my dog.
The result, for me at least, as that my dog only gets to come along if we’re going to all dog-friendly places on that trip. I won’t even leave her in the perfectly safe car for a 10-minute grocery run. I don’t trust people to read any funny or cute sign I make. People are fucking nuts.