The "why" is "greed". By the billionaires, their accountants and lawyers, the politicians, and basically everyone else that hopes someday it could be them. Call it sin, call it immoral, but it comes down to evil people doing evil things.

Remember, good people cannot do evil, because that would make them genuinely evil. However, evil can and often does do good in order to convince others that such is their true nature. It's not, but their acts are sufficiently convincing that they get away with their shenanigans.