Nah, you see it in fiction all the time, extraneous characters that set mood or provide exposition and sometimes, admittedly rarely, philosophical commentary. It's a shame that you don't see it more often in forums. 

I use them all the time on the tabletop. Sure, you can simply have a demon walk into the town and describe him.... but if a harried farmer in a leather skullcap rushes in carrying a torch, wild eyed and breathing heavily, suddenly calls out, "The demon comes! The Demon comes!" and throws the town into panic... then the mood is set and when I describe the demon finally arriving the players are irked. 

Instilling emotion, whether it be tension, heartache or exultation is what a writer exists for.

Edit: Mind you, unlike a movie or novel, there's nothing stopping anyone from walking up to any of these characters and chatting with them or asking Bamf about them :)