No idea. I suspect neglect (as opposed to a conscious decision). 

For a bit more context, I recently discovered that there are several gem-driven features which aren't represented in the Gemfile (e.g. we ran into libshadow the other week), and I haven't seen any guidelines for what's in/out.

Since this is a native gem which many people won't care about, I was reluctant to add it in for realz (which may be why it was never in there). But since I lost a half hour of my life not realizing that we needed *this* gem rather than the fork by the same authors named just `augeas`, I hoped I could save someone else my pain by leaving the explanatory comment.