Quality is very important in a sub-woofer cable (and everywhere else) and my hunch is there aren't many that believe it nor are there many quality-oriented middle-of-the-road ics/cables that will suffice.
I don't know much more than to say that some to many cables and ics produce a deficiency what's known as time-smear.
As I understand it, this time-smear occurs when a single signal enters into the cable/ic and by the time it arrives out the other end the same signal arrives at multiple times rather than at a single moment in time.
Hence among other effects, an ill-defined, muddy, and sloppy bass with no solidity or visceral impact. Just a sloppy earthquake-like rolling effect.
Several years ago, I had just installed the Audience Au24 speaker cables (and still am using) which did much to minimize/eliminate time-smear. At the time, I was using an 18-inch subwoofer and suddenly the subwoofer seemed disjointed from the full-range main speakers.
Audience suggested I try a pair of their inexpensive line of ics, the Conductor series, since all of their cables employ the same technology toward minimizing time-smear.
Sure 'nough, the sub-woofer's bass improved immensely and once again became a natural extension of my full-range speakers' bass. In fact, the difference was amazing.
It's not so much that you need a special 'sub-woofer' cable as much as you need a well-designed cable/ic for all of your equipment and speakers (and sub) that considers the reality of time-smear and does what they can to minimize/eliminate it. Time smear will have similar effects throughout the frequency spectrum. Not just the bass regions.
However, if the bass notes resemble mud, then time-smear in the cables is definitely a potential culprit.
-IMO