They really should, as it adds to the reader's ability to assess trustworthiness. However, qualitative studies can be quite lengthy and the results or even the data itself sometimes requires more space, and to comply with publication/journal requirements, their process or design may be the first thing they cut. I would recommend that if you are interested, simply email the corresponding author, and they will usually be more than happy to send you information or discuss it with you!!
I would also recommend publications such as FQS (available online only) who do not set strict word or image limits in order to promote quality over quantity!
Hope that helps - and remember to always ask for clarification from the author if you need it!
Garumma - there may be several reasons why this doesn't take place. One, as Laura has identified, word limits may dictate - when lengthy, rich narrative findings may predominate. Secondly, qualitative research may be viewed by many 'beginner' researchers as the 'softer' option to study and publish - so may not be that confident in the process that they used. Also - it may be that the more commonly used methodology of descriptive exploratory approaches is used - and there isn't much to say with those; other than content/thematic analysis was used.
I have the impression that at least some part of the qualitative studies are self-explanatory. In my case, it is easier to put in two phrases that I do discourse analysis than to enter in my concrete methodology. This methodology shows through my analysis (as usual in discourse analysis). The other side is: if you explain your method in detail, you become easily attackable - while your study might be sound, methodological (just as theoretical) thoughts are easy to criticize.