I spent some time on business in Japan earlier this year, I needed to constantly remind myself to use the coins in my pocket instead of just letting them pile up like usual. Their two highest-value coins are analogous to $1 and $5, and are roughly close to quarter- and (modern) dollar-size respectively. So, 1. they have coins of value and physical size to make them useful in daily commerce, we don't, and 2. they also don't issue any notes that compete with the coins, we do. As much as I'm an American patriot, I'd like to see us disconnect from the old sizes and take examples from other countries' coins. Then again I'm one of the diminishing number of people in the US who prefers to use cash.