Most wealthy individuals aren't holding cash, they put the money in a savings account or investment that has a return. This money appears to be held to most people, but even money in a savings account makes its way back into the economy by affecting the reserve requirements of banks. Its a proportional effect, because reserve requirements are greater than 0% but lower than 100%, but it still contributes.
If they actually are hoarding, the question is why and in the past that is usually because savings returns and investment returns are expected to be negative. In which case, thats the problem to solve.