Those are for cars with physical keys. In cars where the key switch is only telling the computer "is key present: [y/n]" they put a message on the bus that answers yes and the car starts. But if you're going to use the need for security as a defense then you don't start by designing your car like that.

Some car manufacturers have also attempted to use encryption and implemented it so poorly that it was easily cracked.

There is no technical reason that a car key can't effectively be a yubikey. The computer issues a challenge to the key, answering the challenge requires a secret stored in the key, so you need the key. It works as long as the encryption isn't broken.

And if "car can be remotely controlled" and the encryption is broken then that's a much bigger problem than anything your local mechanic is doing.