I've spent some time with a full frame Canon SLR with a few different fixed focal length lenses. (35,50,&85mm). My favorite lens is the Zeiss Distagon 35mm/1.4 even though it doesn't have autofocus.
That being said, I have moved to the Fujifilm x100v and I'm happy with the results.
Why would they? 35mm is much more versatile and better for family, travel, and street photography, which is what those cameras are used for.