Actually, the reason is that even fermentation doesn't completely break down the glutens in grains. Gluten (and other proteins) can be partially broken and still retain some of their original characteristics.
Originally Posted by Figlio di Moros
If you think of a gluten molecule as a charm bracelet with 100 links in the chain and a charm every 10 links or so, fermentation will break many of the links, but still leave bits of say 2-20 links with their charms still attached. Some of those charms will be the evil, autoimmune inducing charms and they will still have at least some effect in people who are susceptible. That's why celiac's should never rely on any process for removing or degrading gluten. (And actually, the gluten molecule looks more like a wadded up pipe cleaner, but I couldn't come up with a clear analogy based on a pipe cleaner.)
BTW, I drink craft and home brew beers now and then. I love beer and I have no deliberate intention of giving it up, but I am finding that over time, I'm getting less attached to it. Maybe I'll feel like giving it up altogether one day.
CW-125, part calorie counting, part transition to primal
GW- Goals are no longer weight-related