In response to this thread title, why indeed? I am perfectly happy using alternative C41 and E6 that I formulate from scratch, on demand in 1-liter quantity. Looking in my files I find transparencies and negatives more than 20 years old that print/scan close to original--good enough for my purposes as when they were processed, with films from Fuji and Kodak going back to Vericolor II and earlier E6 Ektachromes. That's not to say I don't really appreciate discussion about matching films to processing for optimal and consistent quality. However, images I process today can be expected to last another 20 years at least and that's longer than I expect to care. Archival (> 100 year) processing is somebody else's concern, in my opinion. Important photos that perhaps should be archival, i.e. ones I want to leave for posterity, I shoot on large format in black & white.
For processing analog color, I figure you can never tell when the next meteor is going to hit. It's arguable whether or not any digital will turn out to be more archival than a roll of processed and properly stored film. I can't read code I wrote twenty years ago and have stored on 8"/160KB floppies, but I presume that it's still there. I can still print C41 negatives and look at E6 transparencies and of course too few truely magnificent Kodachromes of the same vintage.
Anyway, that's my take on this thread subject.
(BTW, I use the same quinone/peroxide bleach for both C41 and E6 and am very happy not having to locate, buy, ship, and store Fe-EDTA)
By denying the facts, any paradox can be sustained--Galileo
CPAC (as Ron knows) was set-up by ex EK employees initially to manufacture silver recovery units. They also bought Tura and own Trebla chemistry, they have plants manufacturing chemistry in a few countries now.