why do people feel the need to buy expensive cable

The quotation marks are his, to define the position he wants to argue against. His own view comes with the words Audio signals are AC.....
I am afraid I created some confusion. What I should have writen is:
against the view that cables are directional, Douglas Self answers ' Anyone prepared to believe this nonsense won't be capable of designing amplifiers, so there seems no point in further comment.'

Oops....standby willemj for being chastised for "Appealing to Authority!"

Sure, and very good authority it is.

@willemj Exactly! That’s why it’s an Appeal to Authority. Anybody can round up some expert somewhere who will support your position, no matter what your position happens to be. See, you guys learn something everyday. Even what’s his name knows what an Appeal to Authority is, which frankly is kind of shocking. 😛 Maybe you can find an Einstein quote. It nice that you admire or worship those who agree with you. 🙄

Definition of an Expert. Someone who use to be a drip under pressure.

I have much more expense in my ICs, PCs, and speaker wires then in my electronics. I have all High Fidelity Cables having gone from their initial CT-1 ($1600 for 1 m.) and up to their Pro ($18,900 for 1 m.). Yes, that is right, almost 12 times as much!! I also had an interconnect of their Elite series. It was better than the Pro, especial its bass, but enough is enough! And the Elite weighs 154 pounds in a 6 inch diameter and 37 inches long! Where would I put these?

So where did this investment in cables get me. I should say that other components including my amp, line stage, phono stage, dac, turntable, music server, and grounding unit, also greatly contributed to my sound. But my speakers are invisible and the speaker end of my room is replaced by a three dimensional sound stage with instruments with all harmonics and finger sounds playing them and singers who breath and turn their heads. And all of these have precise locations on stages.

My only regret is that I am 79 and only now have this music with its realism and thrill.