Because those people are already giving most of their money away to causes that benefit the world. The "other" rich people are still, on average, creating weal

Because those people are already giving most of their money away to causes that benefit the world. The "other" rich people are still, on average, creating wealth though, via the companies they start and run. If you disincentivize them from doing those things, you eliminate that wealth, leaving everyone worse off on average.