Well, with block chain smart contracts, all those derivatives and debt swaps would have been triggered and all the money would have exchanged hands already. To the destruction of umpteen trillion dollars.
It is only because of obfuscation, and nobody pulling the trigger, that they remain.
If you do fractional reserve lending, at say 10%. You lend out the money 10 times. If one of those goes bad, you have lost all your money. So, in the realm of smart contracts, you go bust almost instantly.
If a bank / coin decided it was going to do fractional reserve, then the block chain using community would demand transparency on it, and you would very soon see the ponzi scheme of it.
Fair answer. For what it's worth, I bet you overestimate peoples' desire for transparency. Case in point: BitConnect and Tether. Both making billions of dollars in the blockchain-using community with business models that essentially cannot be made transparent. At least one of which almost certainly started as a ponzi scheme.