How much of it do you suppose is based on trade effectively? So, the offspring of parents may feel a debt towards them for raising them that they 'pay back' when their parents grow old. I suspect sometimes, that's why they have children on some level. A kind of living insurance policy to look after them when they're old.
Spouses/ partners will (hopefully) take care of one another if the other falls ill but- it's an agreement/ understanding pretty much- especially in marriage. The nicer way to look at it is that they're in love and don't like to see one another suffer. The same goes for friendship I suppose.
Of course, there are the 'Good Samaritans' out there that just help others because it's the right thing to do.
Really though- I don't have people around me to help either. But I have to admit- do I deserve their help? What have I done for them? They have their own families and friends to take care of- why should they have to worry about me? We're not family. We're not even friends. That's not to say in an emergency, either of us would be unwilling to help the other. Personally though, I actually feel really uncomfortable accepting other people's help because I know I haven't done much to warrant it.
Would you say you've done a lot for other people? Maybe you're not in a position where you can but actually, most people probably can do stuff. My Grandma suffered terribly with her health but, she always found ways to support me. A debt sadly, I mostly didn't repay. I can't say I do much for others personally. I'm pretty selfish. I use the lame excuse that it works both ways. I'm not asking for anything from them in return.
If I'm honest though- if you expect people- especially strangers to go out their way to care about you and help you, you may well end up disappointed. Although, there may be charities willing to help but, they'll likely have to assess who needs it most.
People may care about you on an abstract level. We probably care about one another here on an abstract level but, practical support is a whole lot more. That costs someone their time and money most likely. I think most of the time, that requires a relationship on some level- family, romantic, friendship. Maybe it's cynical to say but, I think that kind of thing relies on an exchange. What will you be giving them to make them want to help? Friendship? Gratitude? Will you support them back?
I think the real tragedy is when there are people who've done nothing but help others in their lives and when it comes to their turn, everyone flees. That's especially sad I find.