You can say they're currency but they're not on a blockchain afaik. That means they can be manipulated/created/removed. I mean, you use it on the site... it's obviously not something you'll go at a mcdo's and proudly show it to the cashier on the screen of your phone. Proper currency needs to have value for everyone. Crypto- stands for Encryption/Encrypted. (Here goes the blockchain and uncompromisability of btc/ltc and whatever else resides on one of those.)