Why is not like going to the shop and paying with cash?
So instead of blocking TOR they should offer things like Bitcoin?
Exactly, the problem (from the seller's POW) with credit cards is that the transaction can be reversed if the buyer complains. If you have a physical delivery address, and you send the cops there to investigate. If your goods are delivered electronically, then there is no recourse. A scammer could give the billing/shipping address associated with the card, receive the stolen goods, and everything would look kosher until the card owner receives their monthly bill and complains. At this point, the store would get a chargeback, and be screwed over.
With Bitcoin (or other cash-like on-line services) there is no possibility to reverse the transaction, no fraud protection, so once the store completes the transation, they have their money, and it cannot be taken away.