I would imagine the NuVinci hubs do wear. But, perhaps they are more forgiving to poor shifting and more predictable with failures than other hubs.

I think the basic IGH hubs have a problem that if one doesn't get a clean shift while coasting, then it will wear the gear selector, and eventually begin to skip. Perhaps also a little finicky with shifter adjustment.

Do they do an inspection all all the bikes periodically? A skipping IGH might only be picked up with a test ride which would be expensive.

Anyway, I would imagine CVT hubs are being used due to an expected better/cheaper fleet servicing that would offset the higher parts cost.