let's imagine that you have a car that you bought for 100,000. it has depreciated down to 50,000 (cars are bar none the worst investment you will ever make). yo uget in an accident. it's not your fault.
you had planned on selling the car on the morrow for exactly what it was worth, 50K, but now your plans are shattered. you get the car fixed up and try to sell again. they now offer you 45K.
in this case i think you can make an argument that you lost out on money. 5K to be exact. I would sue if i we you.
but lets say you hadn't planned on selling it anyway. you drive the hell out of it and years later and when you sell it for 24K it's only 1K less than what you could have got for it had it been undamaged. so... you really lost 1K because of that accident, not 5K right? so, do you pay the insurance company back if you got that 4K difference or do you just steal that money that you don't deserve? that 4K didn't make you whole. that was bonus, and undeserved. see the problem with this? you end up making money off of accidents. you could just go around slamming on your breaks and making money