We need new supply to replenish the lost coins.
There is a common misconception about "lost coins". If you drop half wheat flour in existence into the ocean, it will not be consumed by anyone, therefore it is considered lost-- people now have half of that good than they had before. But, money is never lost; it is only transferred. If you throw $10T into the ocean, the total goods and services remain the same. It's just that, due to decline in money supply, they are priced higher.
This guy is more concise than I am:
Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone.