Because superior agility and tougher skin (calluses) are a bad thing? Besides, I trail run. Scrambling over roots and rocks in Vibrams actually leaves me less vulnerable to injury as I have a contoured surface (including use of my toes) gripping said root or rock as opposed to a flat tread that can slip.
Barefoot and vibrams do not give you superior agility or grip. Callouses and tougher feet, yes, but be fair, anyone will tougher feet by running in most shoes. I'm a trail runner as well, btw, you don't get any more grip than I do.
I'm honestly curious, exactly how is just wearing a pair of Vibrams as I go about my day being a pretentious jacktard? (This should be good.)
McDougal's book is responsible for that fad, and it was filled beginning to end with half truths and pseudo science. Its been almost entirely discredited. Which is why sales of minimalist shoes have collapsed.
Source.
http://www.runnersworld.com/running-shoes/sales-of-minimalist-shoes-plummet
The Tarahumara tribe in Mexico weren't good runners because they ran barefoot, they ran barefoot because they were dirt poor and located hundreds of miles from anything resembling civilization. They were good runners because they started young and lived of a diet of natural foods, not the processed garbage we eat in the developed world.
McDougal and his fans have built up minimalist and barefoot running into sort of a cure all, that all running related injuries are caused by running shoes. Aside from that failing the common sense test, (who would continue to buy the same shoes they kept getting injured in?) its a simple question of physics. If you take pressure off one area, such as the knees, that pressure and stress is relocated to a different part of the body, such as the ankles. Exercise science had demonstrated that you can, will, and are more likely to get injured wearing minimalist shoes for several reasons. First, the human factor. People read Born to Run, and immediately go out and drop 120 dollars on a pair of Vibrams without any phase in, or training, or base mileage, and often no prior running experience at all. Just a jump onto the bad wagon.
Second, because there is so little protection using the minimalist shoes, the bones of the foot and ankle are prone to stress fractures.
Third, I already mentioned. Stress doesn't just vanish, it simple moves from one body part to another. Knees to ankle, for example.
Source for the above.
http://www.ncbi.nlm.nih.gov/pubmed/23439417
Fourth, the attitude that so many(though not all) barefoot runners seem to have. That barefoot running is the correct way to run, because humans didn't evolve with shoes. If you're running in a traditional pair of shoes, you are wrong. Period. And like vegans, they're usually not shy about telling everyone around them. They conveniently overlook a critical detail humans. If something can be improved, we improve it. Modern running shoes are the product of nearly a century of R&D and experimentation. They are not simply, as McDougal puts it, thick slabs of rubber. These are advanced, technological marvels of synthetic materials, they offer protection to the feet from rocks, roots, and biting animals, they wick sweat away, they provide support, they provide grip, and return energy to forward momentum that would be lost into the ground if the human was barefoot.