I'm pretty sure they approached VW to get permission to use their vehicles image's, and were turned down. They were a bit over sensative to their product being used to make some kind of "war machine". Feel free to correct if I'm wrong, or if this has changed since. I've been outta the loop for sometime now. Too busy with new job and family to keep up with all the toys.
That's kina ironic considering all of the kubelwagens they produced for Hitler.