I still think bitcoin is an asset, and it's hard to call it currency.
Because currency is going to be widely used, and bitcoin is hard to use on a large scale right now, I expect the lightning network to change everything.
Actually, you can use bitcoin as an asset and currency. Aside using bitcoin as an asset and currency you can also use it as an investment which will help you to gain and make income. Furthermore, some people prefer to use as an asset simply because they earn income from it but I think bitcoin is more capable to use as currency.