Edit

They're simply not on Metacritic's list of worthy reviewers.

http://www.metacritic.com/browse/games/publication/name

who knows, but they should be added... what ive seen from the game so far looks better than a 7.9 to me.

Trying to understand Metacritics inclusion/exclusion of review scores, is like ice skating uphill. There's really no rhyme or reason. Yet another reason to not really take the site seriously and do your own research.

It's already too high anyway

yeah, metacritic's methodology is just so fucked up.  i like the way rottentomatoes does thing much better. 

In my opinion this is a much better place to get an average score. It doesn't give any site more value and it incorporates every review available:

97 reviews: 8.1/10 average

http://n4g.com/channel/until-dawn/reviews

You can email metacritic if you think they missed out on a score or if you think they have a wrong average. Email your concerns at editorial@metacritic.com

I emailed them before on some missing reviews and they did update.

Because metacritic sucks...

They only count professional journalists's reviews. Nowadays anybody and their grandmas can have a blog and review games on it, but Metacritic doesn't count them. A few in that list I am surprised is not counted, like DualShockers.