This may slide in a small fender bender with a couple of thousand in damage. But, if there is serious personal injury, both your own carrier and any excess you purchase through Hertz will do a deep dive to determine whether there's any basis to deny coverage. And, voila. You've "saved" $10-20/day on a rental and now you lose your house, your savings and whatever else is lying around.

Even if it were ethical, which it isn't, it's a foolish thing to do.