Seems many people treat bitcoin like an asset given how much it's gone up over the last year or so. But some academics disagree with that assessment. If it is to be treated as a currency, it will need to stabilize to be of use.
https://www.cnbc.com/2017/10/24/nyus-dean-of-valuation-says-bitcoin-is-a-currency.html
It can not be considered as currency since it is not yet legalized yet it is not illegal. And also due to the fact that it is only virtual that the government does not acknowledge it. On the other hand, it is an asset that you can trade it for a real money.