Regulators are risk-averse. There’s almost nothing for a regulator to gain by not banning something that could be dangerous that turns out not to be. However they’re going to face significant blame if something bad comes to pass and they did nothing.
So it’s not surprising to see country after country ground the Boeing 737 MAX in light of the tragic Ethiopian Airlines incident. The European Union Aviation Safety Agency has now grounded the MAX. However the FAA has not. Outside of Aeromexico North American airlines continue to stand by the aircraft.