Actually I was thinking about this clipper thing and realized the introduction of electric trimmers had nothing to do with clippers being used less and less. The electrics were actually responsible for straights not being used for trimming anymore. It was more a change in technique by barbers probably in the early 50s. They started using comb and scissors more. The clippers were used for initial cutting kind of like a 1K hone for razors analogy. After the heavy duty stuff was done the scissors would come out. Barbers started using the Scissors and comb to do the complete job and then of course razor cuts started to become more popular where they used the electrics for those. Probably the guys starting out in the mid 50s never did use the clippers to begin with. Mostly old timers who held on to the clippers

I checked my Dorko which has the complete box and it doesn't say anything about self sharpening or replacement blades. You have to be careful because hair can get caught in them and then they pull. As I said before they were never popular with customers to begin with. I imagine that had something to do with their demise.