That's rough to assume IMHO. I don't assume either way, but I think most have met someone who is briliant in one domain but just hopeless on a lot of other things.
How fair would you think if a potential employer assumed from your (hypothetical) incompetence in picking a suitable hairstyle and outfit for an interview that you were not fit for a non-customer facing role?
While it absolutely makes sense to keep your important data backed up, I know people who were great academics in their field and yet managed to delete all their PhD work (before services like Dropbox and OneDrive became common).
If that was the intellectual calibre of the person, I wonder how truly worthwhile the lost work was.