My guess is that he runs something that needs to give automated change. Vending machines, car washes, arcades, etc… Basically, if someone puts a $20 into the car wash but only wants a $10 wash, it’s easy to just dispense ten $1 coins as change.
Coin handlers are mechanically very easy. Coins don’t vary in size and shape, so it’s easy to automatically detect which coins have been inserted, dispense change, and reject coins that don’t match. Paper money sorters are much more complicated, and more prone to failure.