why do people feel the need to buy expensive cable

If the question is about why people have a need to buy expensive cables, then why not ask a more general question? Why the need to buy expensive audio equipment? I don't think there's an actual need, but there is a desire. It may say something about themselves to others, but more importantly it's a self-affirming message to themselves. I deserve it, I can afford it and the world is good! Effectively it's comfort food for the soul.

The purchase of a luxury good may or may not make the purchaser happy, but it does make them happy about themselves. It's an affirmation of how they see themselves and their position in society. It's a testament to someone's economic status and discernment. Notice that the two most common rebuttals to those who question the wisdom of expensive cables are variations of "you can't afford it" and "your system or hearing isn't of high enough quality to judge".

There are volumes of research on why people buy luxury goods. High end audio is a luxury item and within high end audio expensive cables are even more of a luxury. The literature is pretty clear on a consensus view. Buying a luxury item makes someone feel good about themselves. Whether or not the cables out perform lesser priced cables is somewhat besides the point as long as the buyer perceives them as a good value. Whether or not someone else considers the purchase to be a good value is also besides the point. In some cases, external criticism of the purchases reinforces the purchaser's positive feelings.

Listening to music next to someone you love can make the music sound better than any equipment upgrade.

Mitch2, excellent point. It's something I don't think most audiophiles can deal with.

The latest "Stereophile" has Micheal Fremer describing his experience with some of the better/best Tara cables. It seems their top model had to be re-engineered because they weren't an improvement over a previous model. He brings it up to point out that it's not all about price, but actually about what one hears. The reworked cable ultimately, in Fremer's opinion, easily bested the previous model. I don't remember the exact prices but the new cable was north of $40k and the previous model was around $25k. Small but important improvements. There's a sound logic to this way of thinking, but at what point is it aural masturbation?