Because that is what they are , and its Dumpers job?

BEGIN {
   package WhatItDoes;
   sub new { bless {}, shift }
}


use Data::Dumper;
use CGI;
print Dumper( { 6, CGI->new(''), 1 , WhatItDoes->new });
__END__
$VAR1 = {
          '6' => bless( {
                          '.parameters' => [],
                          'use_tempfile' => 1,
                          '.charset' => 'ISO-8859-1',
                          '.fieldnames' => {},
                          'param' => {},
                          'escape' => 1
                        }, 'CGI' ),
          '1' => bless( {}, 'WhatItDoes' )
        };
[download]