Most of these people have passed the stage of caring about the desktop itself. I would say they are simply interested in a bash shell that sits on a reliable, well maintained, stable distro with good community knowledge.

When you spend all your time at a prompt you don't really care about unity vs cinnamon vs anything else.

Debian is stable and has fantastic package management, and Ubuntu builds on that with a vibrant community and wide support. For these users, Ubuntu 'just works' and lets them get on with what they want to do. It's about as simple as that.