most car doors are easily defeated by a car jacker so long as the car jacker has elbows to use for breaking the window. the reason your doors lock when you start moving has more to do with that statistics show that locked doors are less likely to pop open in a collision, leading to more effective crumple zones. many cars that lock above 10 mph automatically also automatically unlock when stopped. i’ve always felt the old school solution of “car goes into drive, doors lock” was fine and that all these automatic systems add unnecessary complexity.