Clearly reality is not agreeing with this assessment? As an example of this counter-argumemt : bitcoin.
In a global economy of some 64 trillion, 42 billion (plus the gold and other precious metals, and many other "lack of faith" stores of wealth) is not even a drop in the bucket.
And even at that, you don't have to have no faith in established currencies to also use bitcoin. I personally don't think the banking system in power now will fail any time soon, but I also can recognize how valuable a cryptocurrency would be to replace it.
'Objective amount'? What it is is an amount, and growing, that feel exactly what you imply doesn't exist. There are clearly many people that have lost 'faith' in fiat currencies, or the central banks that manage them, or the economies behind them, or all of these things, to the tune of the market-cap of bitcoin. How more objective an amount can you get than that?
Of course, with bitcoin, ether, and fiat, you don't need a bank. You can always keep your money yourself. Except with bitcoin and ether the ability to secure your own money is much more attainable for average people.
On the flip side, a lot of people conflate trust in web exchanges or bitcoin banks with the stability of the currency itself. Isolated, you have a reason to trust bitcoin way more than any state actor - its math, codified, and nobody can erase it now. On the other hand, state actors have force of violence if anyone breaks the money. If someone breaks bitcoin with an exploit in the blockchain, you are screwed without recourse. At this point, with the amount of participation it has, the bitcoin protocol should be considered robust - but that also is what translates into its valuation. It is only worth so much because it is proven through its long years of use.