I can give you a partial answer, which is that human intelligence is somewhat slower, which mitigates the ability to crash the entire economy in 15 seconds. That's why a stock market can crash in 15 seconds nowadays, but "the housing market" can't. This gives people some time to do some things about it with some degree of thought, rather than all the agents in the system suddenly being forced to act in whatever manner they can afford to act with 15 milliseconds of computation to decide.