I believe that bitcoin should be called an asset, not a currency. The thing is that bitcoin is not very well suited for making permanent transactions and transactions in the store or on the Internet. Bitcoin has a high fee for the transfer and slow speed of payment processing. For these purposes, other coins are well suited, for example the same bitcoin cache
You have a point that bitcoin be an asset because an asset is anything of value that can be converted into cash. Bitcoin have characteristics of being as an asset, and it is also a digital money.