Bitcoin is not an asset, Bitcoin is money and the definition of money is a currency (ie. a medium of exchange) that can be used as store of value. This means because Bitcoin is acting as a store of value and also because it is in its early stages of adoption, its value keeps growing against fiat making it a suitable investment.
Calling Bitcoin an asset is like ignoring everything else that it offers which are far more useful.
Legal classification disagrees with you. The
classification by the SEC is that it is a digital commodity and has been such for almost a decade now (very quietly so but still, that's how they've classified it), and I don't disagree with it. Its transfer-ability and digital properties sure makes it seem like currency, its properties of limited supply/scarcity actually makes it more so like a commodity.