Doesn't every bank run a fractional reserve? So when Coinbase deposits those reserves in a bank, the bank will lend them and there actually isn't a guaranteed reserve.
Coinbase has a guaranteed sum available from the bank, that part is regulated. If coinbase operated as a fractional reserve with regard to cryptocurrency deposits it would be unregulated and could lead to losses for users if it goes tits up. If the bank fucks up coinbase funds are secure, if coinbase fucks up customer we funds are not.
Banks only hold some of their assets as central bank reserves, but solvent banks always have more assets than liabilities.
For a stablecoin to operate like a bank they would have to issue loans (loans are an asset to the bank to match the deposit created when they lend. A regulated bank also needs a certain percentage of owner's capital (paid up shares/retained profits) compared to how much they lend in case of delinquent loans).
A stablecoin just creating tokens with no backing would be fraud, same as if a bank just credited an account from nothing.
