The profits and good PR (for their respective companies) that would come with banning these transactions far outweighs the money made off of transactions that would be made from keeping them.
This is an effort to stop filesharing/pirating, which would lead to a MASSIVE netgain, and security (future business) for these two credit card companies. Also the companies that have their properties pirated/shared/stolen lean massive pressure on to Visa, Mastercard, and all major banks/credit card companies to do what they can to end pirating.
This is just an obvious business plan, not a government plan, that the main focus is on making money. Anyone should be able to spot this from a mile away.
Privately owned companies are a much bigger threat than 'the government', as their resources, and ability to walk on the fine line of the law are massively superior.
- - - Updated - - -
Probably not at the same time, but the idea to block pirating of property (movies, music, etc etc) has been around for.. well, longer than I have been alive, same as with you.
It just that this problem (for those that are losing out from it) has become much more mass, and popular as it was compared to 10 years ago.. or even in 1995 when I first started downloading movies and music and whatever from the net, for free.
Action has been being taken against piracy for years, and this isn't the first time a major credit service has denied transactions with certain companies.. and yes, businesses do work together to meet certain goals.. it is the business world after all... don't need Uncle Sam to tell them to do what they have been planning to do for 20 years prior..