I wonder if the card companies themselves would be happy with those rules. I don't think it's a grand conspiracy. I think they are just looking at the business and realizing that the amount of money to be made from it (especially with chargebacks) is very small compared to the potential lawsuits/headlines of facilitating child pornography and as a result have been conservative.

If they were forced to allow it then it would give them cover and also their competitors would be as well - so there'd be no competitive disadvantage.