You make a good point. I was naively just thinking of the airbags themselves.
If you're in the business of flogging cars this eventually all gets pointed out to ya usually in a bad way. Rule of thumb is avoid resale cars that have had the dash air bags deploy.
When I hit the deer in the wife's Camry I had it sent down to the best auto body in town. Just 2 brothers (owner/body men) work there. Not 8 apprentice auto body kids right out of high school at the high volume place where Intact had directed. After a few days of fighting over costs, Intact relented. If my wife was handling it, they would have mowed her over and she would have ended up thanking them for their expertise and cooperation.
Regardless, I really slammed this deer so I said to these brothers "what's the story on the bags, why didn't they inflate". Answer: depends on the manufacturer. On the Camry 07, the sensors are located on the frame rail, each side, right at the firewall. For them to inflate, the rails must be forced back past the firewall which would be the result of a very serious impact. Essentially so much damage that the car would be considered non repairable.