In primary publications, such as journals or conference proceedings, it is a common practise not to use the title or designation of authors in the front-matter.
What are the most compelling reasons for not including those information? Or in other words, are there any disadvantages?
I suspect to some extent it has to do with the wide range of available titles and honorifics out there. Moreover, this can lead to rather strange credits, such as the German system, where a title such as "Prof. Dr.-Ing. Dr.rer.nat. Dr.(h.c.) Dr.(h.c.) Dr.(h.c.)" is not as uncommon as it should be.
Keeping to names makes things more egalitarian. If needed, you can always look up a person's credentials. (It also helps to keep things consistent, and easier to track authors and cite papers, if you don't have to deal with titles as well!)
I don't see this as a specific issue about titles, but rather a broader issue about how much information to provide about authors. In principle, there's an enormous amount one could say: for example, one could append complete CVs to the end of each published paper. Clearly, it's important to draw the line somewhere. The journals I'm familiar with typically do this by focusing on two issues: identifying authors unambiguously (people sometimes share the same name, but almost never the same name and department), and providing contact information. Titles and credentials bring up the question of status, and that's tricky because there are many different signs of status. Journals occasionally designate status awarded by the publisher (e.g., IEEE fellows or members of the US National Academy of Sciences), but it can be tricky to go much broader than that, since you need a good explanation of why you are publicly recognizing one person's particular type of status and not another's.
One option I've occasionally seen is to include a brief bio (typically one paragraph) of each author at the end of the paper. This is a convenient way to learn more about the authors, and it lets them each highlight whatever information they think is appropriate.
My experience is that professional fields (e.g., engineering and medicine) title are used more frequently in everyday life and are included in publications (e.g., New England Journal of Medicine and IEEE) while in non-professional fields (e.g., math and biology) titles are used less frequently and not included in publications (e.g., Ann Math and Cell).
