The X Server was designed to be used in a networked environment, with
a client/server model in mind in 1980's, before MS Windows came. The
concepts behind X Server are original and not found in other other
operating systems. It is the X Server concept that makes possible
several very different desktop environments - like KDE, gnome,
failsafe, fvwm2, icewm, mwm, olwm, twm, DyDe, Enlightenment and
others, with each environment having their own wide range of themes.
This is an innovative idea that makes a lot of sense, giving
flexibility and usability to support a wide range of users and uses.