While this might be a figment of my imagination, I feel more confidant in modules that ship with the core than with modules I grab off of CPAN. I know that lots of people use and therefore test the modules that ship with the core. I don't know that about the modules I get from CPAN (though it is true of many of them.) If we shipped everything with the core, I'd lose that extra (possibly imagined) assurance.

--Pileofrogs