NPUs are just kind of weird and difficult to develop for and integration is usually done poorly.

Some useful applications do exist. Particularly grammar checkers and I think windows recall could be useful. But we don't currently have these designed well such that it makes sense.

A while ago I tried to figure out which APIs use the NPU and it was confusing to say the least.

They have something called the Windows Copilot Runtime but that seems to be a blanket label and from their announcement I couldn't really figure out how the NPU ties into it. It seems like the NPU is used if it's there but isn't necessary for most things.