Dan Recklinghausen, HH Scott's Chief Engineer, famously said: "If it measures good and sounds bad - it is bad. If it measures bad and sounds good - you've measured the wrong thing."
I am not a cable naysayer - in fact, if I cared more I would resent that moniker because it presumes that the default is to accept claims of expensive cable amazingness, and that the burden of disproof is on others, whereas I would say the opposite is true. I am a cable skeptic, however, who thinks that if there are improvements to be had from boutique cables, they are heavily subject to the law of diminishing returns. That said, I am certainly open to trying new things so long as they don't cost me an arm and a leg to demo.
If someone hears a difference, great. And if they are happy with their choice, double great. Not for me to judge, especially since I know well that there are people out there who hear much better than I do. BUT, I have observed two phenomena that inform my skepticism of claims by both owners and manufacturers. First, I rarely see people say that they did double blind testing of their cables; it tends to read more like - "I plugged it in and the difference was astonishing!" Second, so many cable companies pour on the ridiculous marketing speak - all kinds of pseudo science and outlandish claims. These phenomena obfuscate the core issues of why and whether: is there a rationale behind the cable sounding better and did you really test to confirm that you are actually hearing what you think you're hearing?
To answer OPs question: cable companies don't post measurements because they make a $h!t ton of money selling cables and measurements don't sell. Cables are incredibly lucrative and facts don't enter into the sale as powerfully as perception. Also, many cable companies do not post measurements because they don't have them, though there are exceptions such as Kimber. See this post here by John Dunlavy.
https://verber.com/cables/
