There isn't a standard they are obligated to follow for preventing someone from starting a car without a key. Just because many companies do something one way does not automatically make it reasonable to assume all will. The entire point of being able to shop around between different car manufacturers is that you may want a vehicle that does something differently. For example, if you are in a place without a lot of car thieves, maybe you'd prefer the cost savings from a cheaper, inferior anti-theft system.

Baltimore can make a standard requiring cars to have a better anti-theft system, but they haven't.

Can I assume what you were talking about is the immobilizer? I thought that thing is everywhere, especially in the new cars made in the last couple of years.