Comment by robocat

> rats chewing up the money

Profit for the US government. Fixed by plastic bills.

Every $ printed but never redeemed is a significant profit (assuming other costs are low like printing).

Especially yummy when countries just want to hoard the currency - same as selling stamps that are never used:

  estimate the stock of U.S. currency circulating in Argentina ... U.S. currency inflows during 1988-1992 totaled $20.8 billion

https://www.federalreserve.gov/pubs/ifdp/1993/460/ifdp460.pd...