If the amount of money was small and finite, one person could hoard most of the entire supply of money, and because the rest of society can’t use their currency as easily to trade, there’s less value in the utility of it. The entire purpose of cash is that it’s a universal store of value so that you don’t have to trade goods for goods and instead trade cash for goods. Nobody would use cash if they can’t ever have enough to purchase what they need in the increments they need.

Disclaimer: this is just my intuition; I am not an economist