Currency is a tool that exists to facilitate economic transactions and though it's value varies depending on the confidence people have in it, your first point

Currency is a tool that exists to facilitate economic transactions and though it's value varies depending on the confidence people have in it, your first point is true. I would say the only difference with Bitcoin is that it's fixed and fundamentally deflationary. There are people who invest in Yuan, Pounds and Dollars. Forex trading is a real thing and I expect it's often dabbled in by the same people that invest in Bitcoin. Though not as unstable as Bitcoin, it's still a gamble, a bigger gamble that most investment given that the only real payout is, as you say, imaginary (as opposed to the possibility of dividends that a stock might give you).