Originally posted by Jonathan Mac 50, 55 & 58mm lenses were considered standard on film. 50mm was usually the minimum for a standard lens. I'm firmly of the opinion that standard primes were made a bit longer than the diagonal of the sensor because they're more useful like that, not because 50mm was cheaper or easier than 43mm.
I have a nice pancake Chinon 45/2.8 and a big fat K50/1.2, both in PK-M mount. I have FF rangefinders with 45mm f/1.7 and f/1.8 lenses. I have never seen a 45/1.4 nor 45/1.2 for FF SLRs. I am very sure that fast 50-55-58mm lenses were made because they COULD be made, whilst 40-43-45mm lenses that fast weren't made because they COULDN'T be made, especially to clear an SLR mirrorbox, not and be commercially viable.
Back in film days, FF cameras were shipped with lenses ranging from 35-58mm. That's quite a 'normal' range. HF (half-frame, ~APS-C size) cameras shipped with lenses in the 24-40mm range (FOV equivalent to 35-60mm on FF), sometimes longer. But for non-SLRs, shorter optics predominated. And for FF SLRs, IIRC fast 58s predated fast 55s and 50s; fast 50s came to rule the field. That was the evolution: get shorter and faster.