I don't really get the obsession with fast lenses, shooting wide open suits a fairly limited range of subjects, and generally lens performance is terrible wide

I don't really get the obsession with fast lenses, shooting wide open suits a fairly limited range of subjects, and generally lens performance is terrible wide open. I have some Zeiss Planar f/1.4 lenses for 35mm, and I basically never shoot wider than f/5.6. Also never really shoot wider than f/8 on medium format Zeiss CF lenses. But I don't shoot stuff that needs fast lenses I suppose. In broader photographic terms (outside of full-frame / mirrorless), f/4 is fast. I suspect that people shooting medium format aren't as interested in having awesome bokeh and a super fast lens with a lower number, and instead care about lens performance in general.