It seems like the big name game companies in Japan that have been around since at least the 90s are all treating their IPs as a chance to create games with bad fanfiction storylines. Squeenix allowed Toriyama to do it to Parasite Eve with 3rd Birthday and Final Fantasy X with FFX-2. Konami has been allowing (or perhaps forcing) various developers to do it to the Silent Hill series after Silent Hill 4. Capcom is already having Ninja Theory do it to Devil May Cry with DmC, but Resident Evil is the most obvious with them.
Starting with Resident Evil 5, the team has been obsessed with the male characters, and go out of their way to treat the female characters like they're nothing more than support characters to boost the cred of the male characters. This is a series that once had the men and women treated as equals. It's at its worst with the poor treatment of Jill and Claire, since while Chris and Leon get to be "cool" and the stars, Jill and Claire have been turned into little more than a mix of damsels in distress and "has-beens."
Their complete exclusion from Resident Evil 6 is the clearest evidence that the team approaches this game and the rest of the series as a chance to force their bad fanfic ideas onto it. If the game was meant to be a proper celebration of the series' anniversary, it would star Chris, Jill, Leon and Claire, since they launched the series. Instead, the team only focuses on the male characters and forces the women to stay out of the game, something you would only see from people with an agenda.
Even if they had statistics suggesting consumers only like Chris and Leon (hint: they don't, in fact all the added Jill DLC to RE5 is proof that she's more popular than Chris), that would be complete bull to pull in an anniversary game. Either all four of them are in the game, or Resident Evil 6 is actually an insult to the series and not a tribute at all. Except, of course, in the minds of Chris and Leon fanboys that have no respect for any other characters, which seems to include the Resident Evil team themselves.
"Without me along, who will heal you when you're hurt?" - Rosa Farrell, Final Fantasy IV