Why aren't new vacuum tubes as good as old ones?

I think you guys are under estimating the importance to WE of reliable tubes and the fact that there was competition among manufacturers.

I heard that RCA used the same machine to make tubes for 50+ years and every year the fittings got looser and looser so the newer tubes lost a bit of quality each year compared to the original tubes. I forget any more specifics but the general idea makes sense to me (in this instance). This is one part of the equation it seems...

It is my understanding the materials have a lot to do with it, but I believe there is an art to manufacturing tubes and even though the same equipment is used there are different people involved in the manufacturing process.

When you guys talk about "better" that include sound quality?.