Benefits Of Using Drum Maps

You can use a drum map to map one MIDI track to multiple different synths, channels and/or notes.  You can name the notes in the drum map as well and view them in the drum pane instead of the piano roll.    And you can save drum maps so that it's easy to recall the settings in the future.
 
That being said, I really don't like the drum map functionality as-is.  I find it to be inflexible, buggy and to have a poor user interface for creating and editing drum maps.  I wish they would make some significant improvements.  I would like there to be a simpler and intuitive way to get a drum grid with note names for Addictive Drums and/or Massive than having to use a drum map.

It is possible to get note names w/o using the drum grid, in a roundabout way. You create note names in the instrument editor, and then select those in the PRV, instead of the default (diatonic).

If you are a drum tweaker, and like to fiddle in the PRV to make things perfect, then drum maps are essential.  Seeing the kit pieces and easily manipulating them is wonderful.  I could not live without drum maps.