Yeah, this surprised me too, given the stated interest in a light-weight, server (no GUI) platform.

But we see this a lot - people jump onto Ubuntu despite not having an interest in running Unity, Mir, upstart, etc, or having a slightly fancier installer, or different schedule on release of stable / long term support versions.

I suspect it's simply that for many people unfamiliar with the various GNU/Linux distros, Ubuntu is the one they've heard of more often. And while most people marvel at the sophisticated package management system, few ponder why the package files don't have a .ubu suffix.