I don't know much about this topic, except for things I've heard over the years, which usually contradict each other.
But, I agree with
@sablebrush52 and have thought it myself. The reason people love old pipes so much is that the crappy pipes have been tossed. It's well known that even poorly made pipe brands can have an occasional great pipe.
Another thing I find true is that it's harder to get "good briar" these days than it was 50+ years ago.
I have heard from well known pipe makers that what they are paying top dollar for today, was just regular briar a few decades ago.
What is the reason for this? That's where the agreement ends. Some say that it takes decades to grow a good burl and uncontrolled harvesting has left less desirable burls.
Others say that the growing and curing process has been hurried to make more money....which aligns eith the prior mention that good briar takes time.
And then there are some who say that the briar sellers are raising prices for unknown reasons.
The only thing the carvers/buyers agree on is that good briar is becoming harder and more expensive to get.
Again, is this due to limited supply, greed, inflation???
Who knows.