The following might be a slight generalization for all fields but something I've noticed especially in the field of Scientific Computing:
Why don't people publish failures? I mean, if they tried some experiment and realized at the end that they tried everything and nothing worked. Why don't they publish this? Is it because such content won't get published or is it because it is shameful to have a failed experiment in a journal alongside prize-winning papers?
I spent a better part of a year working on, what now looks like, a dead problem. However, most papers that I read initially took you to the point of feeling optimistic. Now that I re-read the papers, I realize that I can say (with much confidence) that the author is hiding something. For instance, one of the authors who was comparing two systems, gave an excellent theoretical foundation but when he tried to validate the theory with experiments, there were horrible discrepancies in the experiments (which I now realize). If the theory wasn't satisfied by the experiments, why not publish that (clearly pointing out parts of the theory which worked and which didn't) and save the future researchers some time? If not in a journal, why not ArXiv or their own websites?