What makes you think that "keeping their cash there" is beneficial to any society? I am obviously getting political here, but money for its own sake should not be a goal. Money should be invested or taxed.
Agreed. But there is what should be done, and what is done. I don't think this is anyway admirable, or of any benefit to society, (it's basically taking wealth harvested within a system out of that system) but I do see that it might be a possible solution for a perceived problem that exists for very wealthy individuals.