Why do people just walk away even after being hit by a car?

Not long ago, in front of a crosswalk, a car made an illegal left turn without a signal and was about to drive straight through a red light. At that exact moment, a man almost got hit by the side of the car and ended up slamming his hand hard against the hood. But instead of doing anything else, the man just glared at the driver, ignored the driver's urgent shouts, and walked across the crosswalk and left..
Even if it doesn't seem like a big deal, shouldn't it be better to record the license plate number and contact information before leaving? The driver can voluntarily report themselves to the police station and wait, but shouldn't the victim have at least minimal information if they want to file a complaint or a report?