I don't understand the backup key problem I think. I can't come up with a single example in which a backup key is needed. However, she gave it to her best friend, who's battling a horrible disease at the moment. The reason is that it gives her distraction, joy and laughter at the moment and it is meant as a clear message: "we believe in you, we support you and you will make it." Secondly, no matter how much I like this guy - her lover and no matter how well we manage to switch from cuckold play to being friends, it just doesn't feel right. He is the only one PIVing her and this element is used during sex, but I don't have to give him a physical key. There's a lot more that led to the decision of @TheKeyIsMine12 to deny me PIV things. That chemistry between my wife and I is so powerful.