That's because pretty much every country on the planet has some form of organized search&rescue and emergency medical services. Before that, it was much more common.
You also have to take into account that dealing with other people is much trickier than dealing with animals - and potentially much more dangerous.
Animals are simpler and predictable. There's only so much one can do to you if it gets aggressive - that's by selection, as if you found a wounded lion or other similarly dangerous animal, you'd likely shoot it dead rather than try and nurse it back to health. Can't exactly do that with humans.
Then, at high level, animal motivations are simple - avoiding threats, securing food, surviving. Humans can lie, cheat, rob you, or rape you. On the one hand, most people won't do that. On the other hand, real injuries requiring taking someone in are rare enough that staged ones are non-negligible possibility to consider. That, and acts of opportunity.
In short: humans are dangerous. If it were any other animal, we'd put it out of its misery too.
Fortunately, this too is something emergency services solve - instead of taking someone in privately, you need to, at most, shelter them short-term, and the moment you call 911 / 112, emergency response and law enforcement organizations of your country become involved, instantly granting you a large degree of protection. All that makes being helpful much easier than in the past.
In most civilised countries we actually care so much that we chose to spend a substantial part of our public budget on helping injured humans as a collective.
We care so much now that we are funding programs that put them out of their misery (1), a misery created by our civilized system and compassion communities!
Among the many kind things we did for our first dog, the kindest thing was making and carrying out the decision to euthanize her to spare her what was likely to be months of additional suffering.
That that is taboo for humans in many places is something that I hope continues to evolve. It shouldn't be illegal to treat a family member with the same compassion that we can treat our pets.
You also have to take into account that dealing with other people is much trickier than dealing with animals - and potentially much more dangerous.
Animals are simpler and predictable. There's only so much one can do to you if it gets aggressive - that's by selection, as if you found a wounded lion or other similarly dangerous animal, you'd likely shoot it dead rather than try and nurse it back to health. Can't exactly do that with humans.
Then, at high level, animal motivations are simple - avoiding threats, securing food, surviving. Humans can lie, cheat, rob you, or rape you. On the one hand, most people won't do that. On the other hand, real injuries requiring taking someone in are rare enough that staged ones are non-negligible possibility to consider. That, and acts of opportunity.
In short: humans are dangerous. If it were any other animal, we'd put it out of its misery too.
Fortunately, this too is something emergency services solve - instead of taking someone in privately, you need to, at most, shelter them short-term, and the moment you call 911 / 112, emergency response and law enforcement organizations of your country become involved, instantly granting you a large degree of protection. All that makes being helpful much easier than in the past.