To send a message.
Can you imagine what you can do with thermite to those cars?

Aim for the fuel tank then.
But even without a sound made by the thermite, the message can be loud and clear.

I sometimes do when people try to mow me down at crosswalks with their cars, because they’re busy with their phones instead of paying attention.
I haven’t found something that helps so far.

https://en.wikipedia.org/wiki/Thermite
Doesn’t remove the cars, but sends a loud message.