GNOME, KDE, LightDM, XFCE ...
One of the biggest barriers to "linux on the desktop" is the bewildering array of ... well what *are* GNOME, KDE, etc, etc ????
*I* know what they are. *You* do. But it's one of the hardest things to discuss with Windows users who have no frame of reference.
Especially when distros mess around with their choices over the years ... Ubuntu dropping GNOME for Unity, then reverting. Mint using Cinnamon as default (but you can change that if you like).
It wouldn't really matter a pile of beans until you then move up a bit, and discover that certain programs require a specific Desktop. For example, Cinnamon doesn't have a calendar widget for Evolution. You need GNOME. And so on.
As for developers ... well bad luck if you were writing a suite for Unity, and your target market switches to GNOME.