Panaracer as a Japanese company carved out their niche by hanging on to something old as long as it makes them some money. That´s the Nitto way. And they do it for others too, the Rene Herse ones are made by Panaracer. As the Smoke/Dart are sold out quite often, there seems to be demand. So much so that several other companies do offer new 26" skinwall tires (Schwalbe, Conti, Vee Tire, the Alibaba Chinese ones, Rene Herse, Mars, RiderT1 and the cheapo ones mentoined in the other thread ...).
My guess is that the other bigger brands are just so focused on the next best thing and profit margin that they just don´t care about some old tires, it´s just not in their culture. But the Japanese don´t let things die that work & sell. The last new car for sale with a factory tape deck was a 2010 Lexus (Japan only). 2010!
And if the niche is deemed too small for other players, Ritchey, Spec et al should just see it as marketing outlay. Marketing which targets people with money. People who pay 300 bucks for NOS Onzas or 100 for a new hipster tire. And it would not be unheard of to re- issue old designs. For example Michelin and Vredestein have 60ies car tires on offer and they do look exactly the same as original ones. I bet they don´t make much money on these ones either.
So there, rant ranted and I´m off for a pizza before I yell at some clouds.