Poor Grand Theft Auto city dwellers. They mostly exist so that we can carry out elaborate and ridiculous schemes—for example, schemes that orchestrate fights between the police and NPCs. Because chaos, that's why.
You can add one more method to the list of ways to accomplish said fights, according to this mythbusting video by DefendTheHouse—turns out, if you crash an NPC's car into a cop car, the cops will get mad at the NPC and not you...even though it's your fault. Ha.
Oh, and there are other myths tested in this video too. Just in case you were wondering.
Grand Theft Auto V Mythbusters: Episode 6 [DefendTheHouse]