Ads and Copyright

Never thought I’d say this, but the Super Bowl got me thinking.

Why shouldn’t every advertiser release every print, audio, or multimedia ad they create under a Creative Commons license? Choose BY-NC-ND, and make clear you’re protecting your trademark. Forget the cultural effect — I’m talking pure business: What principle drives someone to enforce the full copyright in a work they’d normally pay millions to get in front of people’s faces? Isn’t it irrational NOT to free up distribution completely? Or am I missing something?