> It seems like a win-win.
It's not a win-win, there's significant risk.
> fully collateralized
This is not true! The underlying asset fluctuates in value and is open to lowering significantly in value, leaving the bank holding the bag.
It's not a win-win, there's significant risk.
> fully collateralized
This is not true! The underlying asset fluctuates in value and is open to lowering significantly in value, leaving the bank holding the bag.
You probably underestimate the ability of banks to evaluate risk. Yes, they absolutely could end up underwater on an asset backed loan, but you also shouldn't assume that you can take out $1 in loans on every $1 of stock.
On Schwab's page, they say: "Schwab Bank, in its sole discretion, will determine what collateral is eligible collateral and the loan value of collateral". So, if you have some recently highly-appreciated shares of AMC for example, they might decide they are not eligible collateral, or only offer to lend you $1 for every $5 of stock.