Nearly all manufacturers do not advertise/exhibit their product measurements? Why?

Of course I understand economics.  It is feasible for me at my age and station to acquire more expensive (and in my opinion) better quality cabling.  You do the best you can.   

Back when I was in my teens and 20s, no one even spoke of boutique cabling.  I was not content with the sound of my system and kept changing speakers and amps.  Smog killed the rubber suspensions in my cartridges in the 70s and early 80s (in Los Angeles) so replacements were made prematurely every 3 years.   I also was married in 1981 and had additional concerns.  Then a critically ill wife for 11 years and a child.  Funds were tight until 1998.  

I did appraise two studios which used boutique cabling, among the other extraordinary studio construction (like my current listening room).  The other 14 appraised studios and comparable studios I inspected generally used pro cabling like Canare, Belden and some other names I've forgotten.  There were a lot of cables in the storage rooms.

David Gilmour's Astoria recording studio used 23 kilometers of boutique cables, how much do you think that cost them.

The way I look at it is specifications balanced with how a component is tuned to suite a specific sound objective. Specifications matter to set a baseline for if it can fulfill the needs of its application but after that, it comes down to individual preference and simply trying things.

One of the things I've learned as a relatively new 'audiophile' is learning how to balance specifications and subjectivity as the main factors. Leaning too far one way or another have been the only times I've been disappointed in products in the past.

The sort of person who bases their purchasing decision purely based on measurements, will also be the person who buys the cheapest product with best measurements.

Why on earth would an audio manufacture want to pursue that customer? Its pointless.

Go buy yourself the $300 DAC from a pro audio company and the flattest measuring speaker. And then convince yourself the terrible sound it produces is somehow fantastic and can not be bettered.

No boutique audio manufacturer wants such people for a customers. 

Because nobody cares much.