Purely aesthetics. There have been many tests where headphone driver output was compared using different cables and in every test the output has been identical. Some people will defend their ego (along with their hearing and amount of damage they've caused to other people's wallets), money they spent on cables that amount to little more than jewelry, or the marketing material of their favorite cable company by claiming that there are properties of vibration that are not measurable (lol).
Here's one such test :
https://www.audiosciencereview.com/...e-audio-premium-headphone-cable-review.22457/
Innerfidelity did a test too using a number of cables including stock cables, Cardas, and different price levels of AudioQuest cables and also found zero difference. They even measured the driver's impulse response and found it identical.
People on Head-Fi are an exception to the norm though. While most people would say cables sounding different is absolutely ridiculous, Head-Fi dwellers will tell you all about how more expensive cables alter the sound in dramatic ways and will call people who think otherwise trolls. That's why people here will post memes of people laughing or eating popcorn in response to people saying that cables don't affect sound.
Generally people will shy away from outright saying that they don't affect sound on here because of the near certain harassment that will result and will provide a non-committal answer or add a clause acknowledging that cables may possess magical powers that we can't measure except with our brains.
One of the reasons why it's frowned upon here is that it has huge implications for a ton of companies and sponsors, and even Head-Fi members themselves.
