If people sudddenly hoard money, they're essentially reducing the supply of money, which means the value of money will go up (as there's less of it), effectively acting as a transfer of purchasing power to the people who are actually spending it at that time. Imagine for instance I do something that generates a lot of value (money), then burn that money (or hide it under my mattress 'til I die of old age). This essentially means I gave "value" to society for free, as I created "value" but did not consume any "value" in return, leaving that "value" I could have consumed with my money to be consumed by others.