Why do NOS Tubes sound better than new tubes?

Back then the Military had a great need and relied heavily on ruggedness as well as quality. Can't remember where I read it, but the article stated that they spend much less time creating the vacuum in modern tubes. Back then, an hour on the vacuum pump, now 20 minutes. I never had a nos tube that was dated before 1940's and they were great. If quality was waning then, hard to imagine how good the tubes from the 20's and 30's sounded.

I have absolutely no idea "why", they sound much better, but I can tell you with certainty that they also last a lot longer. That last factor, plus the sonics; justifies the higher price for me.

Because they were made better.

Before now, I never gave a hoot nor hang as to "why" NOS tubes sounded better. All of the post's have come up with some interesting points. Tpreaves stated that not all NOS tubes sound better. Not all NOS tubes were manufactured for "audiophiles". Many of you act like we're some kind of new breed. Hitler was an audiophile.

Since I couldn't find anything scientific, I came up with theories. The very first "high end" for the public was the "jukeboxes". "Why do you think they sucked in so many nickels dimes and quarters"? It was because they sounded so good. This was due to "high end" parts, including the best sounding tubes. Since there was a large market and demand for "audiophile" tubes, many were manufactured. Those jukeboxes were all over the country in the 40's, 50's, and 60's; and they used tubes, until they went to SS in the 70's and began to sound like crap.

Also Western Electric and RCA in the film industry sought after better sound. Most likely another big profit area.