As recently as 1 year ago, the fed funds rate was 0.2%, which isn't enough to pay the overheads of a bank. Banks don't move fast enough to reinvent their whole

As recently as 1 year ago, the fed funds rate was 0.2%, which isn't enough to pay the overheads of a bank. Banks don't move fast enough to reinvent their whole business and churn their whole portfolio into T-bills on that time scale, and take too long-term a view for "let's just shutter the business when rates go back to zero" to be a business model they will consider. Having a single product - a single account type that is backed by T-bills - is not something regulators will allow a bank to do: all deposit accounts has to be backed by the bank as a whole. However, there are non-banking businesses that don't have these constraints, and some of them are doing exactly what you suggest. They are called money market funds and business is great for them right now. You can get the returns and safety of short term Treasuries in return for foregoing other services your bank provides (physical branches, credit cards) and accepting a minor liquidity risk that the fund could pause withdrawals.