Why is the phrase "including but not limited to" used in conference announcements? There are so many conference announcements that use the phrase 


  the topics of interests include but are not limited to


I honestly cannot understand why such phrase is used. The announcment already lists more than 20 topics and then declares that the topics are not limited to the listed ones.
I have two questions related to this issue:


Why lot of topics are listed if they do not limit the topics of submissions?
Does listing these topics mean that the submissions about listed topics are given higher priority?
This phrase is just standard boiler-plate verbiage.  

The title of a conference is generally too vague to define a community precisely, because different people might interpret such a short phrase in different ways.  Thus, when you are designing a call for papers, you generally try to give a bunch of examples as a way of giving a more concrete outline of the sort of community that you are trying to reach.  

But it's a highly inexact procedure, and the boundaries of communities are generally fuzzy in any case.  Thus, the "not limited to" phrase is included as a less informal way of saying, "If what we described kinda smells like your research, don't worry too much about whether it fits a bullet point, and just submit."