The difference comes down to cost and chance of success. Say you hit a deer with your car and break its hind legs. The chances you can nurse it back to health

The difference comes down to cost and chance of success. Say you hit a deer with your car and break its hind legs. The chances you can nurse it back to health are very slim. Not least because the deer is likely to have a stress-induced response to being handled by humans that will adversely affects it chance of survival. And if the deer survives this, you are going to face a long list of further hurdles. From avoiding starvation, dehydration to avoiding infection. And eventually you would need to reintroduce the animal to the wild. How much are you willing to pay for a deer you've hit to have its hind legs repaired and put in a cast? How much are you willing to pay a professional to nurse it back to health. Because to be frank: if you haven't taken care of a deer before, you are pretty likely to kill it. And the deer is going to be frightened and miserable the whole time. So how much are you willing pay to keep a deer you have hit alive? $10.000? $20.000? More? What's your cutoff? Would you sell your car? I've seen people spend that kind of money on pets. And it isn't always pretty when people squeeze more life out of a suffering pet for their own sake. Now, if you chopped someone's arm off the chances of survival (depending on circumstance) and the willingness of someone to pay for it would usually be quite different.