Double Keys

I returned from the chill of Florida to the chill of  New York. Back to my usual routine. I love to travel but I love to come home. This trip, we rented a car to make it easier for my parents and eliminate them picking us up and dropping us off at the airport. I do not understand why the rental car companies do certain things. When we picked up the car, they handed us the car keys. There were 2 keys on a keychain. We drove away and when we arrived at my parents house we wanted to separate the keys just in case we lost one. That's what people do. They have a spare key, in case of emergencies. As we took a closer look at the key chain, we noticed  that  the ring was soldered closed. There was no way to separate the two keys. If you lost one, you lost both. Does that make sense?