I believe that there are more opportunities to shoot on perforated 70mm film vs unperforated. Hasselblad, Bronica, Mamiya, Pentax, Linhof... They all made holders for perforated film. Hasselblad have produced so many of them that the price has become ridiculous (I bought recently two holders with cartridges for 25 and 29 pounds in mint condition). For some reason majority of photographers do not look at what is around and follow the main stream. But I am pretty sure that if Ilford made a small batch of perforated 70mm FP-4 (as they did it in the past), they would have sold it easily.