[abakker]

Belt drives are also very annoying. Naming conventions are inconsistent and obtuse. Parts materials differ, and a whole lot of stuff seems to be custom.

in Servos and steppers, there are also weird mixes of metric and standard sizes - e.g. Nema 34 motors often have 1/2" (12.7mm) shafts with 5mm keyways. No idea why.

Finding gears or pulleys for my purposes has 100% of the time resulted in some machining and lathe work to take off the shelf parts and make them work for my applications.