Are all of these NOS tube inventories real? How have we not consumed them already?

Tubes in the 40s, 50s and 60s were as common as transistors and all the chips of all varieties are now. Radios, TVs and just about any kind of electronic device were full of them. Radio and TV stations and many other large scale businesses used tons of them. The first computers used massive amounts of tubes. The changeover to transistors, etc. was pretty quick so there were very large numbers of them stashed all over the world. Although only a few varieties of tubes are used in audio, there are still a lot of them around.

People like us who still use tubes are a very small number. As far as tube audio gear goes there is much more of it around now then there was in the 70s and 80s. So we don’t use them up very quickly.

A smaller number of them are never used, or NOS. NIB means new in box. Whether it’s the same box the tube came in, who knows? It’s another marketing point.

Buy your tubes from reputable dealers and you’ll get what you're paying for.

Note that new tubes, or "currently manufactured tubes" for those who are seemingly confused about what NOS actually means

NOS and NIB are descriptions that only apply to OLD STOCK tubes. These terms shouldn’t be used with current production tubes. All of those should be unused and come in a box.

Many current production tubes use the names of the premier tube companies from the past like Mullard, Telefunken, Genelex, etc. All the current production tubes have in common with the old stock tubes are the names they have licensed from whoever owns the rights. The materials and construction are very different.

I’m not knocking current production tubes, Many people like the sound of current production tubes for small signal (preamp) tubes, and they are about the only type you can get for power tubes.