I believe Modern Perl should have a core module ... Why not?

;) Because its not something perl5-porters want to maintain ?

Text::CSV::Encoded
Remove CGI.pm from Perl Core?
http://blogs.perl.org/users/brian_d_foy/2011/03/what-should-be-core-in-perl-516.html
http://blogs.perl.org/users/jeff_thalhammer1/2013/03/fat-versus-thin-core.html
Why Perl does not support database access through core modules?