Could this be one reason tubes (and perhaps records) sound better?


This is not a new finding, rather it keeps cropping up in the hearing literature...
"White noise improves hearing":

https://www.sciencedaily.com/releases/2019/11/191112142926.htm
128x128lesdomes
Hiss and pops and clicks and other forms of tube and record noise are not white noise.
If the signal path is absolutely clean then there would not be any need for the added white noise.  But alas ... our digital gears are full of "correlated high frequency" noise.  Some DAC intentionally have "white noise" added to mask or lessen the effect of "correlated digital noise".  
Hiss and pops and clicks and other forms of tube and record noise are not white noise
It can get complicated. To make a general statement can lead to over-simplification.  Are those "hiss", "pops", and "clicks" occurring randomly?  That's something to think about.


Vacuum tubes ,is just another way to tune your audio system , your whole system is about synergy .
cables , power cords, type of digital design , as well as turntable, 
type of cartridge types all are parts of tuning your system to your sonic preferences .
@millercarbon I am disheartened by your continual hawking of the extremely questionable products of Ted Denny and his Synergistic Research company.  None of the products you mention address white noise, dither or anything else appropriate to this discourse.

The ECT, according to their advertising: " When ECTs are placed on or in an electronic device UEF nano-particles within the ECTs are excited by the components EM fields".  Nano-particles indeed! 

Again, according to their ads, the " HFTs oscillate at high frequencies in response to acoustic pressure in your listening room to compensate for acoustic distortion and correct for phase anomalies by re-cuing your rooms acoustic response to sound pressure." 

Finally, no explanation is given for the PHT, just that it will bring about a " lower noise floor, increased resolution, and improved bass extension with increased air and soundstaging".  This is the same verbiage used by everyone who has ever sold scam products to audiophiles. 

Keep in mind that outfitting a audio system with the requisite quantity of this garbage will be paying multiple thousands of dollars!

Anyone with a modicum of common sense would see through this as the unabashed pseudo-scientific snake oil it is, and you are doing a disservice to the good people of Audiogon by recommending this stuff as anything more than that.