Alternative explanation: NLP is lagging behind what we expect because it is a very challenging domain. Explanations of NLP concepts are nontrivial because fairly complex computational tools are required to get anywhere— smoothed n-gram models, PCFGs, LDA topic models, etc. Like computer vision, it requires a combination of statistics, computer science (runtimes and data structures), and an understanding of the target domain. To understand the basics may require taking an NLP class, reading Jurafsky and Manning, and looking at quite a few lectures (which, yes, are occasionally distributed as PDFs).
