I don't know why you're catching so much flak. Parking lots are not safe places for kids, and you can't leave them alone in the car for long either. I've never had an issue returning a cart, but that's because I've never shopped at a place where the return corrals are that sparse. If it's over a minute's walk to return a cart then that's a failure of the parking lot architects, not you. You're doing what you can, which is good enough.