I will use your own argument, the wealthy don’t sit on their money under the mattress, they invest it usually in industry, so they are helping to create new jobs and opportunities, more effectively than any government. Equally, back in the old days people made their fortunes locally, the6 owned the factory in the village / town / city. These days people make money on the world stage, if you invest in say Google shares, you investing in a company with global reach. Your not ‘hording‘ GBP, but dollars, and they are giving you dollars having made their money in every currency and economy around the world. Equally, who do you think buys up government bonds to enable governments to borrow?
The problem the UK had is that we dont have enough millionaires or billionaires, we need as many as possible! The more the better. Higher taxation on the super wealthy who can literally live anywhere in the world will just drive them to say Monoco, where they d8nt oay any taxes!