I personally don't like the inclusion of mutli-word phrases such as dark chocolate and dumpster fire. I feel like some of the new words don't yet have solid enough meanings to warrant a dictionary definition.
I may be quite wrong..
I may be quite wrong..
So having definitions for these phrases has additional utility for readers in a way that having definitions for "red firetruck" or "trashcan fire" does not. Consider that many users of English dictionaries aren't entirely fluent in English, and might be coming from a language where these metaphors are different or non-existent. For instance, the German word for dark chocolate (because German has compound nouns where other languages have phrases) does not call it dark, it calls it bitter.