If two airplane manufacturers were found to have massive safety issues which nearly led to enormous fatalities (but no one actually died), would you be calling for them to ground their aircraft until safety was made the number one priority?
The people worrying about AI risk are worrying about "it goes wrong once and kills billions of people". That's not a risk profile that allows for waiting to see if the risk is real, you have to prevent it before it happens. It's akin to the risk of the cold war going hot, not even "just" a nuclear reactor irradiating half of europe (which has yet to happen, but is a risk with nuclear reactors, chernobyl got uncomfortably close but ultimately was well contained).
This is the new "nuclear weapons will ignite the atmosphere".
Runway incursions and midair collisions are another example.
Only airliners are required to have TCAS, smaller planes and helicopters don't even need radios or transponders unless in certain airspace. Midair collisions do lead to fatalities, enormous fatalities if an airliner is involved.
Runway incursions and overruns are similar. They cause lots of fatalities and injuries but only the busiest and largest airports have automated systems to warn when a runway is occupied or end of runway (overrun) arrestor systems. Most still rely on human voice to deconflict.