They're not that hard to extinguish, you can just wait for them to stop burning on their own. Which is generally how car fires are also extinguished. The good news is EV fires take a long time to burn through the fuel, allowing anyone in the vehicle plenty of time to safely get out of the car.

Sure, it's a bit annoying for the fire fighters who turn up 20 minutes later... but I think even they would rather arrive to find a burning car if it means the people who were in that car are safely watching from a distance.