If I donate 10€ to the charity it's not much, both for my personal finances and for whatever organization would receive that money to share it with those in need. It's not much and considering I belong to the top 10% of the wealthiest people on earth I should share what I have. Still, I don't earn that much so that I could give much more than that without it affecting my or my family's finances.
Me donating that 10€ is roughly equal to world richest 1% giving out millions. Even if they give out tenfold it wouldn't make any change in their daily lives. And some of them do. Not only tenfold but some are committed on giving away most of their wealth by the Giving Pledge which is to date accumulated over trillion dollars in pledges from some of the wealthiest individuals on the planet.
Bill Gates has already donated over half of his fortune, yet he's still the second richest man alive. His net worth has only gone up so basically he's richer than he was when he started really working for giving out his fortune. It's not as easy to just give away billions.
Even Gates' donations pale in comparison to those made by the wealthiest man in modern history: John D. Rockefeller. During his lifetime he gave away over 500 million dollars, which adjusted to inflation would be more than Bill's and Jeff's net worth combined today. This was still only half of what he had.
The true hero and master philanthropist is Chuck Feeney. This duty-free shopping mogul has given away (almost) all of his fortune after working hard for 38 years to achieve that goal. Only leaving a modest 2 million fund for him and his wife to live comfortably until the end of their days. While his donations might pale in comparison to those made by Gates or Rockefeller the fact that he gave away basically all of his 8 billions is just mindblowing.