Road debris causing damage, to the underbelly or elsewhere is not uncommon (heck, drivers even have to worry about road debris going through the windshield and impaling them, let alone dangerous damage through the underbelly). I would not have wanted to drive your old Beetle in some parts of the United States, particularly not speeding on a highway.

Here's an article about road debris in a normal car (not even your Beetle, where it would have easily killed you): "a sizeable chunk of angle iron that actually tore through the bottom of the vehicle, found lodged in a portion of the backseat." (https://www.westerndirect.ca/learning-centre/insurance-news-...)

The reason the car "needs" to be protected from such damage is the media attention, not because it's unusually unsafe.