Well, yeah, but there are established techniques that are still very finicky. For example, staining frozen sections with fluorescent antibodies can go wrong in many ways and favors the experienced. Electron microscopy can take a lot of training to get right, and also requires careful staining techniques to get meaningful results. RNA work (e.g. FISH) is very sensitive to the presence of RNase which is ubiquitous and difficult to exclude from preparations. So a procedure can be specified that is reproducible but getting the same conditions is more difficult than, say, using Nix.