Attacking industrial systems is not something that 'just any' hacker can do. Not necessarily due to the skill involved, but just because getting access to a system or the software that runs on the system may not be trivial (unlike, say, getting a pirated -- or legit -- copy of Windows).

The gist of this guy's argument seems to be that industrial systems aren't being patched fast enough to plug the holes that stuxnet used. Until these systems are all fully patched, anyone looking at stuxnet can exploit those holes without needing to gain access to the software these systems are running (to find new exploits).