It's true that at one time you couldn't get a publisher to consider your color work unless it was Kodachrome. It is also true that if you shot slides in the 1940s and 1950s and it wasn't Kodachrome, chances are they have faded away by now.
The days of Kodachrome's domination are gone for a variety of reasons. This is largely because competing film manufacturers have greatly improved their product lines. Personal opinion here, but I also think Kodak deliberately limited distribution of all their slide film in the past 15 years in favor of color print film, which has also been vastly improved.
There have been rumors about Kodachrome's demise for at least 20 years, so I'm skeptical about this one. I heard one of the problems with Kodachrome that couldn't be altered or improved upon was that the chemistry involved is pretty unkind to the environment. This in itself could severely affect profitability.
I would like to pass on a note regarding archival qualities. I recently came across a couple of rolls of Kodachrome from 1941, and a couple from 1945. No, I didn't take these slides, it was well before my time. The color and grain was marvelous, probably much as it was when they were first returned from the developer. I don't know the history of their storage life, but quite a few of them had suffered from the dreaded "spider fungus" that grows in the emulsion. I think this is usually from humid storage conditions.
It's important to realize that archival storage is that which occurs in an archive. An archive is monitored by professionals, in a controlled climate environment. The use of the originals is restricted, and duplicates are made for distribution and projection. Even the most serious photographers among us are not likely to truly posses and archive.
I knew a fellow who was a serious photographer from the midwest USA. In the 1950s, before air conditioning was everywhere, he moved to Florida. He told me many people like himself were forced to give up photography because the heat and (especially) the humidity ruined their collections.
No matter the excellent archival storage reputation of a film, if it has been stored in a basement or attic, it is probably junk. Next time someone tells you they know of an old collection of aircraft slides that their uncle took way back when, brace yourself. Might be more of a heartache than a goldmine. If you want to avoid the bitterness and dissapointment you are likely to experience when viewing these old slides, simply send them to me. I'll open a cold one and grind through that disaster for you, heartache free. Tough job, but someone's gotta' do it.