Negative interest rates are here already, in the USA. You even point at it obliquely.

"as long as inflation is higher than interest rates"

Negative real interest rates. Savers already lose money in savings account and even in many bonds. Even before income taxes. The risk free return on capital is already negative.

The only point of bank accounts are logistical. You have to have one to get our paycheck, pension, social security direct deposited. Even if you could actually get someone to send you a paper check if you don't have a bank account you will have to pay a fee to cash it.

TEK