Because you can choose to leave your phone at home and are travel everywhere by car if you don't want to be tracked. But you can't leave your car at home and travel anywhere.

It is true that we don't need cars sending telemetry to track us since there is a conveniently placed identification number on the front and rear of the car, the number plate (used by government), but this is physically broadcasted and that limits its reach.

So why should the manufacturer of my car have access (and the right to sell) a lot of my personal data like location, weight, age indefinitely just because I own a product manufactured by them?

It is an unnecessary overreach on very sensitive data and I can't really opt out (if buying a modern car) since all manufacturers are doing it.

Yes I also carried a phone everywhere the last 20years, but that doesn't make the tracking right (also on phone I think we should be tracked less).

I understand and agree in general, but the root issue is in the laws and what's permitted to companies. Giving your data to car manufacturers and 3rd parties should be mandated to be disabled by default by law and only enabled with proper informed consent.