The really scary thing is that a generation ago it was no big deal to do something like this. My MIL used to stay in the car for hours while her mom and dad were in the bar. My DH had a carpool buddy who told of going to Vegas in an RV with his parents. They locked him inside alone while they went out gambling. Yikes. Parents are definitely held more accountable now, thankfully. I would never dream of leaving my kids alone.
When I was very young my dad would leave my sister and I in the car for hours at a time. No food,just a pot to use if we had to go to the bathroom. It's not like the windows were tinted and nobody could see in. Anyone that walked by would see 2 very young little girls in a car alone. I too am grateful things are much different now.