Even if Bitcoin was not "spent" much it would be useful. Currently in the west people are "saving" in the stock markets. You can't use stocks to buy things, and trades out are taxable events for most of us. And yet the stock market continues to flourish.
Same with gold. Gold is property. And people hedge with it.
But Bitcoin is a better hedge than either really. And the world is *juuuuust* figuring that out right now.
And here is the kicker. Bitcoin's properties make it the most natural electronic money ever. It is DESIGNED for commerce. So once people are in it they will start to move it around. I.E. SPEND it.
So... that's where it gets interesting. How will that unfold? Yes, I *do* think eventually people will spend their Bitcoin. I am just not sure about the path to that future.
And let's not forget why some people think of Bitcoin as part of the "stock market", is that through derivatives, closed-end funds, and exchange-traded funds, such as GBTC, QBTC, BTCC, BTCX, EBIT, BTCQ, and BITC and a few more in the future, you can now get indirect exposure to the price and volatility through your tax sheltered or tax deferred accounts in your respective brokerages.
Not to mention the treasuries:
According to bitbo.io there are at least 1.6 million bitcoin in 62 companies, worth about $75 billion.
I hold bitcoin directly, as well as put some in my retirement accounts (that don't hold bitcoin, but an ETF that claims to hold bitcoin.) If you were an institutional investor, you can't really go wrong with the funds. And if you are an individual investor, you can't go wrong with putting a little bit into your retirement accounts too. It's still best to hold bitcoin directly / physically / private keys, but a lot of people either have difficulty with that or don't understand enough to do it safely.