There is a big difference between missing nonverbal signals, and being incapable of apprehending nonverbal communication. It's a grossly untrue stereotype that people of great cognitive ability lack emotional intelligence and street smarts (social intelligence). Such a discrepancy, savantism, is rare. That many autistic people are savants is another untrue stereotype. Asperger syndrome, one of the autism spectrum disorders, is more common. Like all ASDs, Asperger syndrome is a developmental disorder, not a proclivity.
We live in an age in which incidence of pervasive developmental disorders such as autism (including Asperger syndrome) is on a troubling rise. To help put it into perspective, the autistic population is greater than the population of people with IQs higher than 140. It's much easier to accept Asperger symptoms as "normal" when they occur in so many people.
So why are autism spectrum disorders more prevalent now? The prevailing theory is that autistic people have one of various genetic weaknesses that make them more susceptible to environmental toxins (such as mercury) that impair brain development. Industrialization exposes people to much higher levels of these toxins than in pre-industrial society. Bigger picture: this is sociobiological evolution in action. Social evolution precedes biological evolution. This is just one way in which the industrial lifestyle is affecting our species.