I would see it from another angle:

Bitcoin is not yet a currency (but surely designed to become one, anticipating the Regression Theorem).

So far, it is just a speculative vehicle, an asset, a share, but there's nothing wrong with that. It's a share of a borderless potentially anonymous open and transparently developed value transfer system, eating away market share from the likes of PayPal, VISA, MasterCard, Western Union etc. And you can invest just by holding some of the limited 21 million transfer units, whose value is determined by supply and demand.

But if/when its market share approaches satisfaction and its volatility stabilizes, it will finally become a real money very native to the medium in which it was born, the internet.