Safety Deposit Box Question?

My grandfather is 81 years old and can't find his key, he can't remember where he put it. The bank would not let him in his own box without his key. My Question is why can't the bank open it for him or do you really have to have the key? So what happens next do they keep your belongings or what can he do?
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To open a safe deposit box you need two keys - the person's, and the bank's. The bank doesn't have a copy of your key - if they did, it wouldn't be secure since they could get into it.

If you lose your key (or both of them, since they normally give you two) it's possible they can have the lock drilled out to get it open, but that will cost your grandfather a substantial fee. The bank can tell him how much it would cost.
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The bank does not have his key. That's the whole idea of a safety deposit box - it takes both his key and the bank's key to open it. If he reports the key as lost, they will have to drill out the existing lock (destroy it) to open the box. Not unheard of. He will be charged for the costs of replacing the lock.
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Depends on the bank. Some banks require their key and your key to open the safe deposit box. They can open it for him if he dies and you bring in a death certificate. I am not sure of other ways they can open it thogh
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The fee to drill out the old cylinder can range from $100 to $200. They will make you a new key at that time.