Why didn't Joe Louis and Archie Moore fight each other?

Two reasons: One their primes were at different times. Joe Louis held the heavyweight title between 1937-1949, made a brief comeback and retired in 1951.

Archie Moore on the other hand didn't win the light heavyweight title until 1952, he wouldn't have been a big enough name during Louis prime to get a fight with him.

Two weight. Moore did of course fight heavies but up until around 1944 he was still a middleweight and from until after Louis retirement was a light heavyweight, whereas Louis was a heavyweight.

Therefore they didn't fight because during Louis career Moore was too small and not a big enough name.

Archie was a little later than Louis, so they did not match up during their primes.

i read on another forum that moore apparently stated he respected louis too much to fight him,