i'm one who loves rare/non-mainstream pairs and i read anything that i want to read. only giving up when the grammar, spelling, and format is really bad that i couldn't understand which sentence ended or begin at or when i'm already tired of reading.
i did try to sail my own ship, as in, wrote a fic about them and spazzing to my own fic (i do that a lot and not only on 48-46 fandom).
that's why i always made time for myself to check any forum, be it jphip or ao3 (since ffn didn't allow rpf) of there's any new pairing around.
i agreed with yuki that 48-46 fandom is just a small, small, island on fanfics board in general. but in that small island, those mentioned pairings (kojiyuu, atsumina, mayuki, wmatsui and to an extend sayamilky, yukirena, yuiparu) are mainstream.
i also think that there's a saying that people loves to look back on their old glory. maybe that's the case.