Gnome, KDE, XFCE, LXDE, MATE, Cinnamon, Unity. I find this list beyond frustrating, and verging on absurd.
I tend to think of this as the lack of pipes problem. Every unix tool can be piped into or out of every other tool, and so combined with absolute freedom -- perhaps too much freedom. The choice of shell used to do it barely matters, and can be swapped out easily, so we don't have to ask at install time if the user wants bash or zsh or fish. The desktop developers have not come up with a flexible unifying abstraction (and some even seem to be throwing out the few abstractions available, like separate window manager programs) and so are stuck either imitating the past, or fragmenting in a ceaseless, aimless desire for the new and shiny.
I tend to think of this as the lack of pipes problem. Every unix tool can be piped into or out of every other tool, and so combined with absolute freedom -- perhaps too much freedom. The choice of shell used to do it barely matters, and can be swapped out easily, so we don't have to ask at install time if the user wants bash or zsh or fish. The desktop developers have not come up with a flexible unifying abstraction (and some even seem to be throwing out the few abstractions available, like separate window manager programs) and so are stuck either imitating the past, or fragmenting in a ceaseless, aimless desire for the new and shiny.