Hybrid Track vs. Conductive Plastic Lin. Potentiometer Resistive Element?
I'm not familiar with the field of potentiometer design but this seems reasonably understandable:

Why use a wirewound potentiometer at all? They typically have higher power ratings and are more mechanically robust. On the other hand, they have a bumpy feel when moved, and the output varies in noticeable steps as the wiper moves from one turn of the winding to the next.


The conductive plastic will smooth out the output steps by being effectively a tiny potentiometer connected between each turn of the winding.
A track made purely of soft conductive plastic can wear down with use, making worse contact with the wiper (hence increasing the (effective?) wiper resistance) and also changing the overall response of the potentiometer. My understanding is that this is the limit on the lifetime of common potentiometers.


If instead the wire carries the majority of the current, worn spots will have little effect on the resistance curve (and if the plastic wears out entirely, you now have merely a wirewound pot rather than a broken pot).
The plastic can be optimized for providing a mechanical bearing surface — as opposed to a predictable resistance — as long as it remains sufficiently conductive to provide an adequately low wiper resistance.