Former public defender here. Cops have no way of knowing when they drive past you what percentage your tint is. Therefore, there are regulations in place that allow a cop to pull you over if you are driving a regular car (coupe/sedan/hatchback) and they cannot see the occupants of the vehicle. Most importantly, it’s often used as a pretext for a stop- meaning, it’s a high crime/drug area and cops are playing the odds that if they pull over the car with tinted windows, they’ll find some excuse to search the car and find some other evidence of illegal activity.