You also can't "instantly" transact with Bitcoin, unless you're willing to risk a double-spend. You have to wait for confirmations through the blockchain which

You also can't "instantly" transact with Bitcoin, unless you're willing to risk a double-spend. You have to wait for confirmations through the blockchain which involve fees AND waiting (or really really long waiting) -- if you're going to pay a fee, why not just use the CC network and get it done instantly? At least when you get an auth from the CC network, you know you're guaranteed the money. When a transaction completes on the blockchain, it's still up in the air until the next block is produced by enough people.