If you want ease of transfer and liquidity then you are kind of back to a bank demand deposit, no? Why go the extra steps?

If you want to transfer treasuries, that can be done, too.

I mean conceptually this is just VUSXX (with a lower interest rate probably), but you can buy something online with it through a PayPal checkout page, or send it to a friend through the PayPal app, or send it across borders in seconds. I do think that has value from an ease-of-use standpoint.

Feels quite similar to normal banking products, but I suppose retail banking in the US is so poor, that it might already be an advantage there.