>>More Nikon RF 135 lenses sold than anything else other than the 50mm.
No one ever uses them, they are both too long and too short.<<
I think that's mostly a reflection of the pre-SLR era. Before zooms became so common, just every amateur who bought a camera kit took the kit-lens 50mm, then the next purchase was a telephoto. Once SLRs became common, the shortcomings of using a telephoto with a rangefinder meant that most RF shooters stopped using their long lenses.
When my dad bought a Pentax SLR kit in the 1970s, it came with a 50 and 135. When I started shooting for the US Army in 1981, the standard photo kit in several offices was a Canon F1 wtih a 35, 50 and 135mm, and none of us beginners knew much about what to do with the 35, which wasn't wide enough. It takes a lot more shooting experience to begin to understand the importance of wide angles and how to use them, but everyone puts the telephoto on right away. I had shot years with 50s and a 70-200 zoom before discovering how to use 28s and 24s.
The 135mm lens is a good tool. An easy lens to make, they tend to be the sharpest in the bag. Carry a lightweight one, and you've got it when you need it.