Why is there no Martin Luther King coin?

Recently I was asked why Martin Luther King has never appeared on a United States Coin.  He is the only person with a federal holiday to never appear on coinage. 
King’s best chance for a numismatic spot came was on a commemorative silver dollar .  In 1999, the Citizen’s Commemorative Coin Advisory board made the following recommendation: 
Committee recommends issuance of a commemorative coin honoring the accomplishments and life of Dr. Martin Luther King Jr. The Committee recommends the issuance of 500,000 $1 silver coins with a $10 surcharge per coin. The Committee recommends the surcharges generated by the sales of these coins be used for the purposes of acquiring the personal papers of Dr. Martin Luther King, Jr., the preservation of these papers, and the creation of wide public access to these documents and others related to the Civil Rights Movement.”
This led to the Dr. Martin Luther King, Jr., Commemorative Coin Act of 2004.  The bill was referred to the Committee on Banking, Housing, and Urban Affairs, which is the last we have heard of it.
In the meantime, the congress was criticized by the Citizen’s Commemorative Coin Advisory board for coming up with coins for the government’s own self aggrandizement. Perhaps the nadir of US commemorative coins was the Capitol Visitors Center Coin series.  A coin commemorating a visitor’s center -- holy cheese.  According to the committee: “Enactment of the Capitol Visitor Center program marks the fifth time in 11 years that the Congress has authorized commemorative coin programs benefiting the Capitol, the Congress, or affiliated institutions, such as the United States Botanic Gardens and the Library of Congress.”  But I digress.
While King did not make it onto a coin, commemorative coins were approved honoring Leif Erickson, Thomas Edison, Lewis & Clark, John Marshall (a chief justice -- which I am sure you all knew), Benjamin Franklin, and Louis Braille .

There has been a small movement to get Martin Luther King on the circulating one dollar coin, based on a petition  from 2008.
This is unlikely to occur in the near future since the mint is locked into the Presidential dollar coin series for the near future.  Sacagawea has strong support as the non-presidential figure (the North Dakota congressional delegation will not allow her removed).  Production was recently ceased on the one dollar circulating coin (other than small quantities for collectors)  so there is no demand for another design.  And so, King’s best chance will be to get on a commemorative coin in the future  -- unless he replaces Thomas Jefferson or Franklin Roosevelt on the nickel and dime.  Both of these historic figures are under fire. Texas removed Jefferson from their school curriculum recently, and politicians regularly criticize Roosevelt for alleged socialism.
Adding to the problem is the fact that King was not an elected official.  As a result, his relatives, who run the King Center, insist on royalties for the use of his image.
Martin Luther King was a leader for desegregation, the abolition of capital punishment , and the end of the Viet Nam war.  (Of course, his viewpoints on some issues have been sanitized for modern consumption).  Appearing on a coin was not one of King’s concerns.

1.38 million dollars for a chain cent

A superb example of the 1793 chain cent has just sold for 1.38 million dollars in Florida.  This is a new record for a copper coin.  You can read about the background on the 1793 chain cent here.