I think E*TRADE treats assets in the brokerage account differently. While you aren’t guaranteed against declines in value, you are protected against acts of fraud committed during the bankruptcy of a broker-dealer. Take a look at
https://us.etrade.com/e/t/estation/pricing?id=1209025020
for more information about protection limits (it deals with more than just their conventional bank accounts).
What do you mean by that? Are you saying that trouble in their banking business wouldn't impact the brokerage customers?