> Adult content, pharmaceuticals and travel are all industries that experience significantly higher occurrence of fraud and chargebacks than others. For example, your spouse sees a weird item on your credit card for a porn site. "Wasn't me! Must be stolen I'll report it." Sometimes it's the other direction.

No, it has nothing to do with chargebacks. It's not even presented that way in their policies when they ban it. They consider it a "brand risk", which is completely different.