why do people feel the need to buy expensive cable

I like red wine but I tend to buy more moderately priced bottles because I can’t taste that much of a difference between mid-priced bottles ($10-$20) and higher priced bottles (+$25). There are bad low priced wines and bad high priced wines. But I would never say all high end wine is a rip off or call wine connoisseurs misguided as that would show my ignorance.

I am slowly upgrading my audio cables and like wine I do so based on MY senses, not others.

Purchasing decisions are made from various reasons. Necessity, sense of style, sense of accomplishment, appreciation of craftsmanship, pride of ownership ...  It is my observation, usually says more about the ones that criticizes the decision than the ones making the purchase.

When it comes to taste, we humans use a fraction of our genes available and it's NEVER the same ones used from one person to the next, nor the amount. That accounts for why some have phenomenal tasting abilities and some, like me, don't. There's a lot of overlap but it's never the same.

That accounts for the widely varying abilities of some to be able to nail it each and every time. The same goes for visual acuity, tactile acuity and hearing acuity. We're not all wired the same. 

I've seen blind tastings with wine and it all boils down to what suits your tastes. It's an immediate and undeniable process: either you like it or you don't. There's no penalty to it unless it's your job to be able to identify and quantify (those jobs can pay very well). 

Visual acuity can be rigorously tested and affirmed due to it's nature. There are standards that cannot be denied. I've yet to see any A/B testing of visual acuity let's say from one brand of TV to another as a means to deny the obvious advantages of having a better picture to watch.

Hearing acuity is a different animal but, again, we're not all wired the same and no amount of parlor tricks can refute what we can or can't hear. This has been debated ad nauseam here and elsewhere. Granted, there are snake oil salesmen out there but there's some honest manufacturers as well. 

Enjoy what you like and ignore the naysayers. It's possible they can't hear the difference. 

All the best,
Nonoise

Because the cables are usually better.  How much better depends on what makes your ears happy and how much you willing to pay