Hope your not refering to military and your talking about a specific company because I have a lot of concuring opinions from the 2.
I hope wherever you work they take it seriously and dont allow materials off site.
I don't know why you say it this way. I did get my clearance as a result of military service. And I don't get what you mean by allowing materials "off-site". The Military does take classified materials to locations that are "off-site" because sometimes their work is "in the field" and not always from within a hardened and secured facility. It doesn't mean that protective measures aren't taken, but the job has to get done and sometimes it's done by small teams from remote locations.
As for the military's relationship to corporate espionage, there are two major angles to the issue;
1st is the "Actor" and althogh the military, or I should say DoD, may not care about corporate espionage against a company like Google for instance, State Sponsored espionage is always their concern.
2nd is the target, Government Activities, Employees, etc, Military targets, National Infrastructure, Financial Institutions, Defense Contractors, Companies involved in protected information like encryption services or proprietary information that could be used to damage US Business interests in the global marketplace are all important. The DoD doesn't just exist to protect itself, it exists to protect our nation and it's interests in the world.