Why do banks keep some money in reserve rather than loaning out all their deposits?

The same reason you would put money into savings for yourself. For emergencies.

For example The U.S is currently taking money out of the reserve to help with Coronavirus relief

donald carl johanson (born june 28, 1943) is an american paleoanthropologist. he is known for discovering – with yves coppens and maurice taieb – the fossil of a female hominin australopithecine known as "lucy" in the afar triangle region of hadar, ethiopia.

hope this !

i googled "who was kolson johanson" and this is the answer i found.

sorry if this is incorrect.

me on my last question.