Would you prefer the $6 on the left or the 50 cents on the right?
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Independent Accountant nails it in the comments.
Through 1964, U.S. coins were actually worth something. They were made of silver, with approximately 0.72 ounces of silver per dollar face value (dimes, quarters and half dollars had weights and silver content in exact proportion to their face value, so a quarter weighed 2.5x as much as a dime, and 1/2 what a half dollar weighed).
Once the Federal Reserve had debased the currency to such an extreme that the metal value exceeded the face value, the mint stopped making coins of valuable silver and started making coins out of nearly worthless copper-nickel alloys. That debasement continued so far as to make a penny not even worth a penny's weight in copper, so copper pennies were replaced in 1983 with copper-coated zinc.
With spot silver at $17, that 50 cent piece has about $6.12 in silver content, while those six copper-nickel dollars have a metal value far less than the face value. And that face value is guaranteed to lose purchasing power over time.