Another problem is that Uncle Sam does a poor job of informing the public just what sorts of coins are current. Maybe there should be posters in banks, post offices, etc., informing the public of the types of coins that Uncle Sam's mints are producing? On a similar vein, recently at a Japanese shop I tried to use a Japanese 100-yen coin from 1975 commemorating the return of Okinawa. But the clerk refused to take it, claiming that it was "foreign". And I've run into people here who seem to think that the oversized Japanese 500-yen coin commemorating the 100th anniversary of the "Cabinet" system of government is just an oversized game token.
The Okinawa commemorative 100-yen coin is standard size (between nickel- and quarter-size), while the 500-yen coin is the size of a half dollar, versus the standard 500-yen coin which is the size of an Anthony dollar. I guess people don't want to accept coins if they're not familiar.