After nearly a decade of converting & riding ebikes, I have yet to witness a single battery fire issues myself.
I've heard of them in the news, interwebs, etc.. just not witness any.
In the early days for ebikes, they were lead acid batteries that cause fires.
Nowadays with lithium battery fires; I suspect they are just poor wiring job or charging practices.
Personally, I feel that strapping a container of flammable fuel on to a vehicle and travel at 50-60 mph isn't much safer.
How many car fires occur daily? fuel tank explosions in the news?
I'm sure there are plenty of those occurring every single day, just don't get as much attention and don't reported all over the interwebs.
Regardless how much you regulate with laws, doesn't change the fact that gasoline is flammable fuel that is meant to burn while the vehicle is in operation.
The sheer number of gasoline engine operating in the world allow us mankind to feel that gasoline cars are safe and okay to be used in the billions.
If the same number of ebikes are operating (as gas vehicles) & ebike batteries are exploding at the same rate of gas tanks explosions around the world; would you feel any safer?