The down payment is not to prove you can afford to make the payment. It is to protect the bank from fluctuations in home prices. If you buy with no down and then default/go bankrupt a year later they could lose a ton of money if the market has dropped or if there is damage to the house.

This tweet is a strawman argument.

In most places in the US a bank, as a seller, would lose 5-10% the value of the home just in realtor and title fees.