The problems are:

• it is not what theme designers requested - they wanted templates for thing like login page
• the renderers api is not stable yet - we can not declare this api public yet

We could reintroduce this later or it is also possible to add it into just one theme.

IMO this is not supportable in the 2.0 and should be removed from HEAD. I would personally prefer if we tried to introduce some sort of real templates in 2.1.