Wrong direction of trust...
You have to start by assuming everything is suspect, so the PC/OS should start with the assumption that any USB device cannot be trusted.
As others have mentioned, when it is plugged in the very least an OS should do is tell you what class of device it claims to be. If it should be a USB mass storage device then that is fine, and you can proceed to be suspicious of its contents.
However, if your USB stick claims to be a mouse/keyboard/etc then WTF?
Fine for a proportion of El Reg readers, we might go "WTF? ...disable... ...destroy..." but that is not good enough for Joe/Jane Public for whom the OS needs to be a bit more protective, and query with language a bit more obvious than "enable HID?", say to something like "You appear to be adding a second mouse, is this really true? Think carefully my friend before answering..."