I suspect a percentage of the 40% don't believe it's possible, or believe it would end up being 0.5% of their income to enrich a select few (as has seemed to happen with previous attempts to "save" entire countries).
Some people also think that we should spend that money on other stuff that they’re interested in like cool space stuff and just don’t care about poor people and never will.
Poverty is a relative concept. Even among billionaires, there are poor billionaires that would find it painful to give up any part of what they have.
Mind you, they still think poverty is bad, but they'd object to something like paying for basic infrastructure and be happy to create the modern-day equivalent of CCC camps to pay the poor people to build that infrastructure. That sort of thing.