Well, everything has upsides if you don't compare it to the competition. Even if cars were incapable of transporting people, you could say the upside is, they're a good source of scrap.

But, compared to the competition (buses, light rail, bicycles), it's hard to see where cars come out ahead. They are more expensive than every other option, they produce poisonous fumes, they take up enormous amounts of space, they only work for able-bodied people, they are loud, dangerous, and absurdly wasteful.

I don't think they are worse than smoking as a public health risk. But when you consider the amount of pollution they produce, it's likely comparable. And smokers are taxed - while car drivers are massively subsidized.