Ah, ok, I thought you had never even seen locks like this. I'm younger than you guys

, but it has also been a while since I had a car with these types of locks. I remember that they used to be round, similar to the ones in the picture, while other (more recent?) cars used the same mechanism, but the knob was a flat plastic widget.
Naive question from somebody who always owned closed cars: Aren't door locks kind of pointless on an open car? What would stop somebody from simply reaching inside and unlocking it, no matter what the mechanism is? I guess an alarm might, but that could just as well be triggered by somebody opening the door.