Why did Romney put the dog on the roof? Is there any good reason to do this?

I just can’t get my mind around that story of Mitt Romney putting his dog on the roof of the car. It seems to me that if one is setting out on a 12-hour car ride, and one has to choose between (a) putting some luggage on the roof or (b) putting the dog on the roof, any dog owner with a functioning brain and heart will choose (a). I don’t see how anyone who can’t figure this out could possibly be qualified to run a corporation or hold elected office. I’m not just being partisan here—this story really baffles me. So am I missing something? I’ve never tried transporting an animal this way— does it actually work better than I assume? Is there more to the story than most news stories told us? Or is it as bad as it seems?