Rising influence of quantum mechanics
Macro-scale style machinery isn't suitable for the quantum world one needs something more exotic instead - wrong
Via a very simple estimation it turns out that nanomechanics is actually barely mechanical quantum-mechanics. Baffling? The fact that quantum-mechanics is called quantum-mechanics is just a somewhat unlucky result of science history. Basically mechanics was generalized to the point where it also encompasses the behavior of electrons thus to the point where it encompasses what is in eveready language considered electronics. And electronics are pretty quantum mechanical at the nanoscale. Of course certain nanomechanic systems can be made quantum mechanical in behavior if the conditions are made extreme enough.
Actually under conditions expectable in advanced atomically precise production devices nanomechanics is pretty classical in behavior. Since the objective is to transport stuff from A to B in a controlled manner just like in makrotechnology using makro-style-machinery (with some minor tweaks) makes perfectly sense and has even advantages such as superlubrication and dissipation sharing.