Current tube Manufacturer's as good as NOS Best

I have been reading with interest many of the posts on tubes and have come to the conclusion that NOS tubes from 40 -60 years ago sound better than tubes from current manufacturers. Why is that? If that is the case then why hasn't some manufacturer come out with a tube that competes with or betters the old stuff. It would seem that with the current popularity of tube equipment someone could come up with a better product. Curious to hear some answers.

Search the archives; much discussion. Basic answer is cost of R&D and tool-up not recoverable with low volume market at present.
What Swampwalker sez, and not all NOS tubes sound better than current production. There is a lot of crap out there disguised as NOS (including a lot of used pulls) and there are some excellent new production tubes. And there is a lot of NOS hype created by those who sell them. You just have to get to know what you need and what is available before you wade in with your checkbook.
There are some new companies that are out to beat NOS quality. Check out Euro Audio Team. Hifi+ magazine gave it a Product of the Year Award in issue 36. They compared their tubes to the reviewer's precious NOS tubes and were shocked to find the new EAT tubes winning hands down. Arthur
Spotty mix here, some NOS are better, but a LOT are very noisy. Some NOS are very good, and some are excellent, and some you can't listen to.

Sound like all things audio, let your ears lead you.

one good explanation I've heard and realize is that in old tubes was used "Clophen" a dangerous substance wich is forbidden nowadays. IMHO.