Suppose for example that we have a ladder in space and it has zero translational motion, but non-zero rotational motion and non-zero angular acceleration around its center of mass. The ladder is rotating faster and faster around its center of mass while having no translational motion.
There is no question that you have to apply a certain torque about its center of mass to produce this particular angular acceleration. A real life example is the specific torque needed for opening a door with a certain angular acceleration. This specific torque is produced by a specific combination of (a): Magnitude of external forces and (b): Direction/distribution of the external forces acting on the body.
Now let's take the exact same force distribution acting on the ladder but take the torque about an arbitrary fix axis in space outside the ladder. This will produce a torque about that axis with an amount that we can calculate. But what is the meaning of the torque about an axis outside the body? Is there practical real life examples where torque around an axis outside a body apply? Is it useful in certain theoretical calculations?