We don't know the reasons between this decision, do we?
My guess would be that it is tightly related to their choice of materials and the decision to optimise mechanical durability while optimising weight and improving weather resistance.
Cheers,
Bernard
It's hard for me to believe that the Zeiss or the Samyang or the AI-AIs are considered as of inferior build quality… This is further proven by the previous series of Nikon's own "D"-series of lenses, where neither the 17-35, nor the ("beast") 28-70 or even the latest versions of 300 f2.8Dii & 400 f2.8Dii where of lesser build quality (some consider them even better) with respect to the current lenses that replaced them… IMO, it has nothing to do with lens design choices or materials… it is only a matter that they judged at the times where the G series of lenses started, that they should follow similar to Canon Eos mount solutions (ergonomically), because they thought that the customers would judge the existence of the aperture ring as being "anachronistic"… although the ergonomics were the same as they are today and could even provide more solutions to the experienced user of the lens… In other words, they simply thought that the existence of the aperture ring, would "scare" some new comers and other "basic" users off… So, they decided against the more experienced user who could find use for it… Let alone that they "killed" the compatibility with their own older cameras and thus they damaged (Nikon did) the appreciation they had among them….
I believe that they (in Nikon) would never had abandoned the D-series of lenses, if they
knew the photo/video imaging convergence that would follow, …it is clearly a misjudgment of things. What is surprising is that they don't consider to resurrect the D-series of lenses, but they insist on the G-series. They could clearly make the more expensive lenses and the primes that address to the creative market with an aperture ring (D-series) and only make the cheaper lenses without an aperture ring… Look at how much simpler the DF would be if the modern lenses would have an aperture ring. Funny thing is, that many of their lenses still in production are of the D-series and in many of them, they retain that stupid "AF-via an axle" design, which reduces the MF performance of the lens considerably than if it was MF or if it had an internal AF motor (AF-S system) in the lens. Nikon's lens series is an ergonomics mess as it is… new comers or people that are "changing ship" to the firm from other brants, need a tutorial on what lens does what!
If they would have only integrate the (much better) AF-s motor and would have worked on improving the DOF scales window on the lenses to gradually replace the ancient axle type focusing, they would have avoid all this mess and the lenses would have many more appliances as well full compatibility with the past cameras… As it is, they loose many customers from buying their lenses (and cameras too) and so do the "independent" lens makers that provide their lenses without an aperture ring.
