I think of abandoned cars as an extra-large form of littering. The cars are simply garbage left behind by someone who couldn't properly dispose of them. I love seeing an antique car restored to its former glory, but leaving a vehicle to rust and fall apart in a field somewhere, that's just useless to me.
I think they can be picturesque. I have taken photos of some. The contrast of the rusty metal and the bush land or grass growing around an old rusty vehicle has an appeal to me. I particularly like it if a plant is growing up through the rusty vehicle.
I think that the rusty old cars that can be seen in the outback are definitely picturesque...in the same way that old abandoned homesteads and other relics of the pioneering days are. Life is so harsh in the bush and there is an unusual beauty in the crumbling bits and pieces from the past that are littered in many of these places.