In the RC car world, I've heard of people having their workshop go into flames from batteries that were simply in storage... not charging or anything.
I keep mine (RC car batteries) in a special, fireproof box when they are not in use, and also charge them in that box (as it's designed to be).
Not an easy way to do with this larger, e-bike batteries, especially when those batteries are built into the frame of the vehicle (some e-bikes and pretty much all e-scooters).
I guess anything is possible, but you are right that most of the time, there is a reason.
Realistically, the EV/e-bike industries will destroy themselves if they can't come up with safer battery tech that won't kill your entire family.
At some point, everyone will have multiple e-vehicles in their home, office, or parked in an underground/above ground parking garage.
If something isn't done fast, these cases of fires will be so common that people will accept them as "normal".