A: There are a couple ways that a cop can take a car or other vehicle from somebody. It can happen if they’re taking the car away from an accident, the car is being towed, the car is stolen (or the cop has enough of a reason to think that it is), whoever was driving it is arrested (and the car is related to the crime.), the person that owns the car actually asks to have it impounded, if it’s illegally being stored somewhere, if it seems to be way too dangerous for a regular road, or if the cop has orders to take the car away.
B-C: Cars and other vehicles shouldn’t be put down on the inventory if they aren’t actually being impounded. If it’s being impounded because of something illegal, there is gonna have to be a reason given on the report, and if there is a hold on the car/vehicle.