I don’t think anyone assumes anyone is hoarding cash. It’s just a time to deployment question.

A dollar flowing into a wealthy person’s account may take a week or two to get loaned out or fielded into an investment, and another week or two to pay the investment manager or begin facilitating the purchase of goods and services. A dollar dropped into an empty checking account may buy food that day from an establishment which will sweep it out to a supplier the next day.

Our financial system is efficient, but the last time I saw a statistic for the figure, it takes about two weeks for the average checking account deposit to get turned into a mortgage.