why do people feel the need to buy expensive cable


I have tried expensive cables and one's moderately priced. I would say there were some differences but I can't actually say the expensive cables were better. IMHO I believe a lot of people buy expensive cables because they don't actual trust their ears and are afraid of making a mistake. They figure the expensive cables are better for the fact they cost more. If you have a difference of opinion or share the same thoughts, I would like to hear about it.
taters
Two of the speakers I used to own are internally wired with Supra Ply. I tried Supra Ply SCs and the sound was okay. Using different SCs sounded better. It's not always the case that what's used inside a speaker is good enough for use as SCs.

All the best,
Nonoise
Some might find this Cable Snake Oil Antidote interesting with respect to LRC, the signal and the system.

Cables affect the sound and the effect is system dependent.

Another's opinion on a cable in a vastly different system may not be valid.
There are two very easy ways to debunk outrageous cable, "power conditioner", "isolator", "speaker cable suspender", "special capacitor", and "special resistor" claims:

1) Measure the electrical and acoustical signals with the allegedly improved "product" versus without. It's the year 2018 folks. We now have cheap devices that detect all aspects of sound (phase, pressure, frequency) at a level that is orders of magnitude better than average human hearing. What once cost tens of thousands of dollars in testing equipment can practically be obtained for several hundred with a high performance laptop, high quality calibrated microphone, and audio test suite freeware.

2) Research the backgrounds of the individuals who own and run the companies that are peddling "special resistors", "speaker cable suspenders" and the like. I've been observing this scam for nearly 4 decades and every single "manufacturer" of said products I've looked into is run by con artists and fast talking salesmen/women.  Just like there are tons of con artists peddling miracle health cures, there are and unfortunately probably always will be con artists selling magic cables and capacitors that some how fix everything that is wrong with your audiofool system.
Someone needs to use the Yellow Pages to find his local consumer protection agency representative. I’m sure he’ll help you mount a nice big lawsuit against all these scam artists. Bad scam artist! Bad! Let us know how that works out. Also, try getting a hold of NASA to see if they have time to do some testing for you. Report back your results.