I had a 2-day rental on National a few years ago, including a free day using a UA coupon.

While parked, someone ran into the vehicle (more than $1200 damage).

The credit card paid for the damage ($500 deductible on my policy), as apparently did the errant driver (never heard from National again). I purchased no coverage from National. I'm still holding the $500 in a trust account waiting for someone to claim it.

Now, I don't know what would happen if the entire rental were "free", as in the case of buying a tour package. I suppose if an appropriate card was used to buy the package, then that would count.