The Pardon Power and the President

The other day, the Washington Post ran a tough editorial, criticizing President Obama for "neglect[ing] his power to pardon" (HT:  Sandy Levinson).  A bit:

. . . In fact, no modern president comes close to Mr. Obama in meting out mercy so rarely and so stingily.

In his first term in office, Ronald Reagan signed 250 pardons for federal inmates; George H.W. Bush authorized 77 and Bill Clinton, 56. Mr. Obama granted just 23. (Including more granted this spring, his total is now up to 39.) . . .

To be clear:  President George H.W. Bush should have granted more, too -- as should most governors -- and I have thought this for a long time.  But, I would have thought that this stinginess would be a matter of serious and widespread regret to those who supported (as I did not) the President during his campaigns and who were moved by his campaign appears, themes, and rhetoric.  What's more, the President has shown himself not only willing to use, but enthusiastic about using, his executive power in order to achieve substantive outcomes that he thinks Congress is unable or unwilling to deliver.  Why not here?