I don't know why, do you? Before I start, let me emphasise the idea that if something is important enough, it can be explained simply and without big words.
In order to give an answer, you can try to understand the question, understand who it's coming from and why, what factors determine what they write. I'm a human animal standing on a spinning sphere, I am able to wonder about things and I have a computer where I can type stuff. I do things, maybe because I have motivation for doing them, or maybe because of habit, or maybe for no reason at all, my urges come and go. Also on the sphere are people who are in serious pain due to malnutrition and fear of death.
It is very easy to help the starving people of the world. At the moment, I can't tell you exactly why it is your or my prerogative to help, but I know it is. One way of thinking about it is to think about what would happen if you saw a starving child enter your room or saw them on the street,
it may be difficult, but if this person walked into your room right now, what would you do?
You would give them some food probably, unless you are wicked like that killer in the texas chainsaw massacre. This person exists and many like him exist too, they may even reach a point where they can't eat because they are starving so badly and they throw up whatever food they are given.
So ask yourself, why is it the difference in this person's location that makes you want to help them?
Maybe you've never thought about it. Imagine if this person walked into your room and stumbled up to you saying can I please have some food, imagine right now, you could touch their ribs and their arm bones. Then you say, I don't care I'm not givin you any food, I'm goin to the movies and get some maccas and the twenty eight dollar popcorn combo, you can stay here and go on the net if you like but you better get off my computer when I get back. Then when you come home he's still there on your chair, so eventually you tell him to get out, maybe you'll have to call the cops or just pick him up and chuck him out on to your lawn if he won't leave. Then you find him dead on your lawn and you have to call the ambulance and tell them you found him on your lawn the next day when you go to work.