My answer to all this is: is there something that musicians cannot now do,
or can do only with difficulty, which using an X/3 meter signature would
enable or make easier? I can't think of any.  Musicians are used to reading
tuplets, tuplets developed as a result of patchwork solutions to practical
problems over centuries, just as most other aspects of notation did.  These
things hang around just like the QWERTY keyboard, for no other reason than
inertia.

Chris Bonds