It's a lot easier to predict a particular technology than it is to consider and explore all the secondary ramifications of that technology.
Plus, in many cases, that isn't even the goal. For many science fiction works, the objective is to examine the modern condition through the lens of a different setting, and introducing too many new factors is not merely irrelevant, it's detrimental and distracting. In a lot of stories, particularly short stories, the ideal is to introduce only one major new element, leaving everything else largely as-is, in order to focus upon how that single element would influence and change us.