How long did it take CPAN to get that way? And I still prefer my native OS to handle packages better than some random developers; that's one of the big reasons I chose it (Debian, for the record). Good developers aren't always good sysadmins. Add to that NIH syndrome, and you get things like Gems.
I can understand cross-platform stability and one-button ease of use, but quite frankly, I've already got one-button ease of use (apt-get), and I long ago gave up on proprietary software that doesn't meet my needs (handling packages properly being one of them).
As for Emacs packages that haven't been packaged for my distro yet, the Emacs library itself is huge (hell, org-mode is now standard!), so if a package needs more than a repository checkout, add to load-path and require to get started, I'm going to have to question its quality.