When building a multi-configuration job, there are tasks which should be executed in the "parent" job only. The example I have on hand (but I am sure there are others) is the JIRA notification plugin.

Currently, when a multi-configuration job executes $n child jobs to satisfy all of the intersections of the axes, each one of those child jobs updates the relevant JIRA issue so you end up with $n JIRA updates that are essentially all the same. I think it would make much more sense for only the parent job to do that update.