A sudden loss of
oil pressure under high-power conditions is going to do damage no matter how fast a buzzer or driver reacts. It becomes a true idiot light: "You just blew your engine, idiot!"
A warning would be for the spectrum of lesser conditions where the indicator and the driver react fast enough to prevent damage. It's a "might as well" item.
A system that monitors RPMs and
oil pressure and cuts the ignition in case pressure drops away while at speed would prevent damage - but only if the driveline wasn't forcing the engine to speed. It could also be fatally startling to the driver.