Many of us have been encouraging cPanel to include Roundcube into their system but they have been reluctant because the software has been in beta or release candidate for the last couple of years.

It is now considered "stable" as of a few weeks ago so we have our fingers crossed if they will release it as part of cpanel.

I suggest some votes for it on their bugzilla if you want a nicer email interface.

Here is the link to the cPanel bugzill for Roundcube webmail. make sure to vote and add comments if you want it added.