Just from the readings, the only thing I could find was here: http://msdn.microsoft.com/en-us/data/jj613668 which stated:
Self-Tracking Entities can not be used with Code First models
While that may not be a big deal, MS has put a pretty good investment into this with their Fluent API and is now the recommend approach to modeling your database. This is very much (almost identical) to how all DB work is done in a Rails environment with
There are also some advantages to using their Fluent API such as versioning your database changes and being able to standup/migrate changes to a new DB simply by running the update-database commands. So, it might make sense for MS to not recommend something that disallows the use of this new technology.