Problem with this is the feature that is used by some external actor once every 18 months. You'll pull the plug, and when 6 months go by, you'll think you're safe. Then when shit blows up, you'll have no context and spend 3 days tracking it back to the "pulled plug"

Because when trying to sell the application list of features is longer, which means we know what we're doing and are able to maintain it.

Because management decisions ain't always driven by logic.

The simplest reason may be attachment to the feature--the feature is of no use but the person who's invented it is scared by the possibility of removing it.