Two Keys
Hertz wants to sell or return the car to the manufacturer (if a repurchase car) with both keys and the owners manual.
The cars move from location to location, if the car starts its life in Orlando, it could be sold in Dallas. (That wasn't always the case.) The "Do Not Remove" bag in the trunk will sometimes hold the owners manual. If the car is returned as repurchase they will get a deduction for missing manuals and only one key. (Manual 75.00 and up, key 50.00 and up, up UP) Not to mention floor mats....
Back in the good old days, the extra key and sometimes the manual would be kept at the originating location because they would be responsible for sale/repurchase. I think Hertz got tired of mailing those items all around the country. JMHO