Black people in the US constantly fear being killed or harassed by police. Yeah, burning a car doesn't solve anything, but keeping quiet and playing ball since the civil rights movement hasn't really moved the needle. Policing and constant surveillance of black communities has gotten worse since then, and protections for police, both legally and politically, have increased. Sometimes you have to burn a car or break some glass for the nation to pay attention.
Also I would say that the initial reaction of rioting is what drove people to organize and peacefully protest, and in a lot of US cities and states, the combination of these has already resulted in policy change. I'm sure most of these people are also posting on social media and planning to vote as well.
I guess this is a long winded way of saying that torching a car is small potatoes compared to government sanctioned murder and oppression, and this kind of thing is forcing people to pay attention and have conversations about this stuff.