As https://bugs.python.org/issue33257 and
https://bugs.python.org/issue33316 showed, Tkinter is broken, for both
Py2 and Py3, with both threaded and non-threaded Tcl, since 2002 at
least, and no-one gives a damn.

This seems to be a testament that very few people are actually
interested in or are using it.

If that's so, there's no use keeping it in the standard library -- if
anything, because there's not enough incentive and/or resources to
support it. And to avoid screwing people (=me) up when they have the
foolishness to think they can rely on it in their projects -- nowhere in
the docs it is said that the module is only partly functional.