I've always been curious--what's the use case for the backlit keyboard?

At the surface, backlighting seems largely aesthetic to me; I have muscle memory of my keyboard layout and do not need to reference the keys at all while in the dark. (A huge tactile cue is the TrackPoint in the keyboard.) I understand that there are lots of variables: not everyone uses their machine as frequently or may not have a keyboard amenable to this.

Does anyone here feel backlit keyboards are essential? Why or why not? What is the consensus rationales?