I started using Perl because it was ported to everything and consistent across platforms, unlike shell script. It may have been several years before I was aware of CPAN -- I don't remember, because that was a long time ago.

I'm not intimately familiar with other languages' packaging systems, but from what I know, they seem worse. For example, Ruby Gems are catastrophically stupid, combining the thing that downloads modules with the thing that locates and loads them on your local machine. This is just begging for complexity and security problems. Perl's simple directory hierarchy for storage, and multiple clients for installation, are a much better solution.

EDIT: Perspective from a real sysadmin. Basically, "you are not a special flower, so don't require your own special packaging system."

EDIT 2: I briefly thought "just use an existing CDN rather than a custom set of mirrors," but realized that it's easier to get people to donate mirrors than to hit them up for money to pay a hosting company. Without a corporate champion, that's kind of important.