Fuji has always been a good lens (and camera) manufacturer.
I'm no expert but perhaps it has something to do with the design of the lens?, most lenses nowadays has an internal autofocus motor, but very few have an aperture control ring as it usually built into the camera.
This means more moving parts and a more complex design, more so if you want weather sealed lenses.
Perhaps this is why they made their lenses 'bullet proof' as they foresaw this and designed lenses that will stand the test of time.