It’s a thing I noticed from self observation. My fantasies about a billion dollar windfall are things like provide free high-speed internet to the populated parts of the world. All of them. It takes about $30 billion to feed the entire human population for a year (mostly freight). A smaller package would be to become a (figurative) god in Haiti by unconditionally rescuing them from a handful of humanitarian crises. A bronze statue of you would be in every public park there for centuries.
There are very real sometimes globe-spaning humanitarian projects that billionaires could afford with a signature (if costing them a Twitter, more or less) that would leave a mark in history dwarfing Carnegie or Rockefeller or Nobel or Gates. And we have thousands of billionaires and not one is trying.
Leeja Miller did a video ( on YouTube ) on how the usual charities billionaires use do actually very little, and they could do way better paying that money as taxes and letting social safety net programs and public science do those things instead. (e.g. Philanthropy is wholly a grift.) So yes, we have zero billionaires doing anything with their money but hoarding it like so many boxes of unused pogs and Funko Pops in the garage.