Which ones are you talking about, Colby? The WT101? I'd imagine it's because the shoe is so thin in the forefoot that you couldn't run rocky trails without it. They'd fall apart. After wearing mine for about 5 months (~200 miles?) they feel pretty flexible. But as I have to wear insoles in them to make them fit, I can't really tell you how the shoe itself really feels.

The NB WR10 (the new minimal road shoe), to me, seems pretty similar to the Altra Intuition.

I'm a little frustrated b/c I haven't found a minimal shoe yet that I don't have to add insoles to just to take up room. Need to take care of my tendonitis so I can get some distance in my vibrams.