investing is risky which means if you invest it in the wrong industry or wrong in a wrong way you might end up with a huge loss.
Both saving money in a bank and investing it are equally good and bad. Banking might seem more secure but you only lose in the long term because of the high inflation rate taking place. Additionally, investing in the wrong area is also bad. I'd rather invest than to save in a bank, and I'd rather invest in both gold and bitcoin.
I think somehow we all rely on banks for now because we do not know what to do of our lifelong savings. How can we put it all in a bitcoin wallet as it is more of an investment right now, if it falls, lifelong money will be lost and no one should take that risk, ever. Once it is adopted and used more like currency and considered less of an investment, I'd put all my money in my bitcoin wallet.
You have always gold, it fluctuates, but is less risky. And you have the fiat paper rectangles.
Bitcoin does not depend on fiat money in any way. It is free market, private money with good money properties.
There is some logic to what you say, because currently fiat money is more liquid than bitcoin, and you can therefore use fiat as an intemediate money type. But you talk as if bitcoin is unusable when there is no fiat money. On the contrary, when the argentinian peso dies, noone will want them, and bitcoin will shine.