[Vigilanteman]

A skilled hanging has the advantage of being generally painless AND a paying proposition. The rope, inexpensive to begin with, can be sold by the inch after the fact.

[AEMILIUS PAULUS]

Plus daguerreotypes can be sold depicting the crowd and the execution. Thus, the state can obtain some reimbursement for the expense of keeping the offal alive until justice is administered.

Being serious for a minute it is simply a lack of will resulting from excessive tenderness. In short, improperly directed pity. See Aristotle and Spinoza for a good discussion of pity.