Digital technology currently allows for the generation of images, which are virtually noise-free (provided the right sensitivity and lighting settings are used). However, many photo edition programs, and specifically the devoted to B&W conversion, do include utilities and functions to add a similar effect to traditional film grain. What is happening here?
A basic search on the Internet might provide the answer. Photographers, who started with chemical techniques working in development laboratories (I include myself in this group, at least as amateur), do reckon specific characteristics y the textures and surface effects obtained with thie chemical process, even more visible with big enlargements and / or "forced" development. Search and achieval of the "right" grain was an art, with the basic tools (focusing lenses, temperature and timing controls...) available.
On the other side, there are some other photographers and graphic artists that use grain to obtain specific visual effects, closer to the prints of the great photographers from a few decades in the past: Apart from being a tribute, this would confirm the validity of the artistic concepts, shifting images away from the basic photographic capture of a subject.
However, currently we are facing an interesting inflection point. First "digital" generation are starting to have access to this kind of advanced processing. This generation was born with Internet, cellphones, game consoles... and with full-color lives: from clothing to toys to television. They don't have this reference from lab development, not even of black and white television.
For this generation, film grain could be just a drawback of old-fashioned technologies... so that nowadays' artistic proposals with this "retro" look could not be valid or appealing for the public, in just a few years... Maybe those proposals will remain as that: an "old" art.
I guess this is a similar case to photography a couple of decades ago: even when sepia processing was (and it still is) widely used, only few photographers produce images with ferrotype or cyanotype effect, in spite of being those relatively easy to produce with the current computer tools available. Those finishing are just outfashioned.
Anyway, and speaking about fashion, I guess the use of added grain will appear and disappear cyclically. As mentioned before, it will be ineresting to see the evolution of photography in the next years. Me, personally, I still prefer to have some grain (added) to portraits, to soften the focus... What is your opinion?