I call this a somehow mental disease. The need to accumulate more and more even when you realize you can't spend that in hundreds of years. The fact that some people are accumulating that much wealth and don't share some part of it with their poor neighbors is that they simply don't care. They are in a constant race for accumulating more and more money, properties and what it is called wealth that they don't look anymore at poor people. Nobody ever said that one who earns lots of money should share some of them with the less fortunate but I would do that. People are for endless reasons. They might be sick, they might come from a poor family that couldn't offer them a proper education and the tools to earn more than they do and that's not to be judged. It is not to be judged the fact that the tycoons are not sharing their wealth either but if I would be one I would do that. I always gave to poor people as much as I could afford it and I always thought that if any of us would share as much as he can with others it life on Earth would be much better. We would all live healthier and happier and in harmony. However some are blind to the poverty of others. They are blind with their own will somehow. The race for more money and power has blinded them and it keeps the blind. The ego is something that gets "inflated" very easy when one has a lot of money and in some cases that ego might think that he is somehow superior to others and that the others deserves to be poor because they're not doing enough to earn more. The wealthy ones very often consider themselves as somehow superior to others and they can't lean to that level and help the less fortunate. Not all of them are this way though. There are a few, not many, that donate money on a regular basis and share their wealth with others, but unfortunately not many. Now if we could look at the situation from a spiritual point of view every one of us has a karma, or a destiny that needs to be fulfilled and if ones karma is to be poor while the other is meant to be rich and wealthy that's what it is and that's why one doesn't hep the other. From our individual level of understanding and our consciousness level it is obvious that we should all share as much as we can, but from a higher and deeper understanding everything has its purpose and it was meant to be that way. Even poverty and wealth and their relationship.
That's how I see this situation. Hope you will find my answer insightful and wish you a great day!
Firstly, I would say greed is the main cause of this. People amassing wealth unending for a lifetime while others are suffering.
Like the saying goes "human needs are insatiable", I believe everyone has that tendency to also be greedy, packing up wealth for themselves. It applies to me and you, we tend to think that the more wealth we have the more we are far from getting back to the ground, so we continue to amass wealth for ourselves.
Also, when you have a lot of money you tend to want to live a life that measures up with the amount of money you have and this makes you begin to spend more and your taste to earn more begins to grow as well. In this case you rake in more money for yourself to meet up the needs you have leveled up for your life.
To the main issue, why do some have enough and they watch others suffer?.. Sometimes you can't help everybody, even those you try to help might not be grateful. Like maybe the person you're thinking about that has that kind of money and he's not helping the people around him might one way or the other help them without your knowledge. Most of them give out money to those poor around them and other stuff but I don't think that's the best way to go about it, because the money will always finish. Instead of giving them fish teach them how to fish and they will never disturb you or look for help from you.
I've seen rich people who always try to help poor people, but everyday those poor people remain poor because you didn't teach them how to make the money your just gave them the money which will eventually finish..
However, I believe everyone wants to amass wealth for themselves but we should always remember those behind us. So they're not left behind.
Hope my answer was helpful? Thanks
Love of money is the root of all evil. There is a saying that man needs and want is insatiable, the reason is because the more wealth they amass the more they will want more, nonetheless they forget that nothing we bring to the world and there is nothing we are going to take back..