I agree, even Nikon and Leitz do not keep parts for a long while , even if they do not yet melt their lens innards into a plastic package. And other renowned makers have disappeared .
However the lens mechanics company Novoflex provided me with a new Zmount adapter for their 60 year old Pigriff, at a cost comparable to their ordinary prices, so it is absolutely possible to make spares if your machines and your directors are flexible enough and your original designs allow changes-
I maintain my view that the processes shown provide cheaper products in exchange for shorter useful duration, especially if affordable repair are required.
p.