It's somewhat common to find a schematic that calls for a germanium diode in amateur radio contexts. For example:
This is a QSK circuit from the Fldigi manual.
And yet, purchasing a germanium diode is a relatively difficult task. For example, Mouser's offerings from 600 manufacturers doesn't seem to include a germanium diode:
(Although, they do have a few germanium BJTs)
Germanium diodes can be found elsewhere, mostly from surplus or specialty stores, for a cost orders of magnitude higher than most other discrete semiconductors.
Why is it so common for amateur designs which do not appear to have any particularly stringent performance requirements to call for a relatively expensive diode not available through commodity channels?