He still has a right to diminishing value because a car that's been wrecked isn't worth as much as one that hasn't. It's not a matter of depreciation or the cars market value, it's about the value of a car before and after an accident that wasn't his fault... If someone kicked your bike over, wouldn't you want compensated for the damage? If I was looking at bikes and one was pristine and the other has been involved in an accident, I wouldn't pay the same price for both. That's why people pay for insurance.