Do you think gold coins have been popular for 2500 years by accident?
Why yes, you're right of course. Just this morning I bought my usual cup of coffee with a gold doubloon.
If you like to think of current day usage of gold as non-niche, that's fine by me. That's just terminology. My prediction is that the current financial system might undergo subtle changes as the result of bitcoin saturation, but that I don't buy the idea that we're going to live in an inflation free, zero-taxation utopia of Randian proportions. In that sense bitcoin's current purpose will remain "niche", even if it will be widely adopted.
You actually most likely paid for your non-fat latte with cash, coins or notes ...
You're blinded by your frothing rand-hate trip ... take a look at the coins and notes in your wallet, that's what fungible money looks like (they are the modern poor cousins of gold coins).
Fungibility as a desirable property for money driven by market demand is not going anywhere any time soon ... no matter how many digital databases the financial facists create to kill it.
Come back to the table with something substantial when you can see past your smart-ass?