Fares at Orange County/Houston Airports

Why is it that everytime a commercial advertises a special low rate for airfares, they always end with the small print indicating that the rate is not valid for Orange County’s John Wayne Airport (SNA) or Houston’s Bush International Airport (IAH)? What’s so special about these two fields that they cannot offer discounted values? I have flown into and out of both airports many times and, in my experience, there’s absolutely nothing unique about them that would force full fares to be enforced.

Asking around, some opined that these two airports were mostly used by business travellers who didn’t care about prices since the whole amount was expensed to the company. I doubt this since both airports are in the middle of million+ population regions and there is no reason to believe that a lower percentage of the people would be travelling for non business reasons than at any other major city. In fact, SNA is within 50 miles of three other airports that don’t have these restrictions.

Could it be due to Orange County’s recent bankruptcy problems where they are not allowed to reduce fares since that would lower the amount of taxes going to the county? If so, what is Houston’s reason?