On what car do you _need_ the remote to enter and drive the car (having tow the only alternative to e.g. the remote battery dying)? In all cars I have used, you could just use the physical key if the remote failed.

My wife certainly doesn't know how to unlock and start the car without the "keyless" function. Every time the fob runs out of battery, she needs step by step instructions otherwise she's stuck there. She uses and sometimes programs SQL and API calls at work, but knows next to nothing about cars.

In addition to being able to break in and steal anything that’s kept in the car

One don't need any keys or other equipment for that. Glass is really fragile unless armored with foil.

And still most thieves don't even bother with doing that, they simply walk around and find a car that was inadvertently left unlocked.

Capture the lock as they walk into a store.

Take the car while they are in the store.

I'm not sure this attack allows starting the car itself.

This is not that. Keyless radio and remote start radio are typically two different systems.

Even more nefarious is preventing the victim from using their vehicle as a refuge or escape from a dangerous situation such as an attempted murder or kidnapping.

Might make for a good movie plot -- but if someone is putting that much thought into premeditating a murder, there's a lot more straightforward ways to trap someone other than elaborate hacking scenarios.