The answer is pretty straight-forward. Every time we tried this before it collapsed into a giant ball of flame.
Nothing crypto is producing is new.
We've had stablecoins before in the form of wildcat banks. [1] They were backed at some point by barrels of nails with a few flakes of gold on top, and what little gold there was, was spirited around from bank to bank in front of the inspectors. That ended predictably.
We've had "ICOs" in the form of blue sky securities. [2] Companies that did nothing sold on the premise that you could simply sell the shares to someone else for more money. That ended predictably.
We've had "high yield investment platforms" in the form of actual honest-to-goodness Ponzi schemes before. That ended predictably.
We've had free reign access to leverage to buy more securities before - it led to the Great Depression. We had rhypothecation of securities and totally baseless collateral generation before - it led to the Great Recession.
Crypto hasn't created anything new fundamentally, it's just re-hashing all the stuff we outlawed before because it was an objective breeding ground of fraud and crime and grift. The only thing new about the crypto economy is that the pitches are structured as "${previously_failed_idea} except on the Internet."
[1] https://en.wikipedia.org/wiki/Wildcat_banking
[2] https://en.wikipedia.org/wiki/Blue_sky_law