It's also an asset which earns them interest. Or in the case of the article and the Credit Suisse/Archegos situation, an asset they leverage to make really dumb moves with (and possibly fraud) to screw over pension funds and others in the process of their greed.

> most deposits can be withdrawn on short notice.

Except for the fact that person A deposits $X in the bank and person B has $X withdrawn, nothing physical happens. It's just an offset on the books and enables them to keep very low cash reserves.

"As of March 2020, the minimum reserve requirement for all deposit institutions was abolished, or more technically, fixed to zero percent of eligible deposits. The Board previously mandated a zero reserve requirement for banks with eligible deposits up to $16 million, 3% for banks up to $122.3 million, and 10% thereafter. The removal of reserve requirements followed the Federal Reserve's shift to an "ample-reserves" system, in which the Federal Reserve Banks pay member banks interest on reserves that they keep in excess of the required amount." [1]

[1] https://en.wikipedia.org/wiki/Reserve_requirement