In wild excess the vulgar breast takes fire,
Till, buried in debauch, the bliss expire.

Oliver Goldsmith, The Traveler (1764)

The verb debauch means to seduce into a betrayal of duty, so when we speak of drunken revelry and libidinous license as debauchery, we should understand our words in the light of betrayal.  A drunken revel is debauchery because, or when, or perhaps insofar, as the men and women who are drunk and reveling ought to be doing something else.   Libidinous license is debauchery because, or when, or perhaps insofar, as libidinous license causes neglect of duty. Read more of this post