To maximize social developments, we reward those who create value for the society. If someone, via their own efforts and without stealing/fraud, generate a lot of wealth, they would have invariably added value to the society by creating a win-win for the buyers, employees and themselves.
When however someone born to a rich person inherits wealth, they are at an unfair advantage for something that they did not really accomplish, and not for any value they added to the society.
The world should aim to equalize opportunity for everyone (irrespective of who they are born to), and then reward them when they create more value than others from the same opportunity. Agreed that defining "equalized opportunity" is hard -- what all would it cover, health?, edutcation?, etc. However, even with some challenges here, this may be better than the current system.
The "use it or lose it" would make the wealthy put money back into the system, and automatic adjustments would result via supply and demand balancing. I understand that it would also increase wastage, and this would need some thinking through. My gut reasion however is how much money can the super rich really use and waste? Ultimately, even items bought by them but unused may be reusable by others (who ideally should not be their hiers at 100%).