Weight and portability. I never used super telephotos to begin with. I had the 16-35 f/4L, 24-70 f/4L, 70-300 f/5.6L, 50 f/1.2L, 135 f/2L, and the 100mm f/2.8L Macro and have gradually replaced them with the EF-M 11-22, 18-150, 55-250, 32, and the Sigma 56mm