I don't think anything is being held back. It all comes down to the simple fact that it is very hard to predict the future, particularity when trying to extend new technologies forward (i.e. robots in the 1960's). I don't think that many people appreciated just how much computing power a robot would need back in the day.
Another thing not to loose track of is what scientists predict for the future often varies greatly from how entertainment industry portrays the future. Take space travel - we've known (scientifically) since day one that there are many very difficult technical barriers to space travel - notably, the amount of energy it takes to get off the earth, but also the extreme distances even "close" objects like the moon are at. Even in the 1950's and 1960's, many scientists were predicting that humans may never leave the orbit of our planet - and so far they have been right. In contrast, popular media at the time portrayed space travel as something that most of us would do, circa 2001...despite the fact that the experts in the field were saying it was unlikely.
The pace of (current) technological advancement is stunning. One example from my own field (biology) - DNA sequencing. A decade ago we were able to sequence sections of DNA a few hundred base pairs long, and were just gaining the ability to assemble those pieces together en mass to make genomes. Seven years ago we completed the human genome - a project that took 13 years and cost 2.7 billion dollars. Fast forward seven years, to today. We can now sequence a humans genome in a week, for a cost of ~$30,000. New technologies being released as we speak may reduce that to a day, at a cost of $5000 or so.
SEVEN YEARS.
Bryan
