>>3807052Because 20MP are enough to print a large magazine spread and resolution isn't the main advantage of larger formats anymore. Since a large format sensor would be insanely expensive and yield worse results than a sheet of 4x5 in most cases. The point of larger formats is having wider field of view and camera movements without overly complex optics.
Also video related:
https://www.youtube.com/watch?v=SIEMuvACO1o 