While not applicable to other areas, I know that conference papers in CS (and many journal articles as well) have stringent page limits. Thus, given a short amo

While not applicable to other areas, I know that conference papers in CS (and many journal articles as well) have stringent page limits. Thus, given a short amount of space, you have to prioritize what goes in the paper. Secondly, when writing an academic paper, the primary goal is to keep the reader/reviewer interested. That is why proofs, simple calculations, and other such "trivial matters" are relegated to appendices -- the flow of the main paper should not be disrupted by these. Finally, one advantage to omitting steps is to ensure that the reader is putting in effort to understand the concepts. Fully drawn-out text would invite people to do conceptual "copy-paste," which would cause problems when they try to apply their knowledge to real-world problems. An analogue of this phenomenon is seen on the web with php programmers, who frequently copy-paste php code found from various tutorials without really understanding what's going on. However, for in-depth tutorials published online, I agree with the author that super-detailed texts are best. And here, the practical issue of the time spent by the author typing, checking, and revising the tutorial starts to become the dominant reason why tutorials aren't so detailed -- at some point, it's simply not worth the author's time.