the monopoly car companies have on their cars is one of the ways they fleece consumers. It's why they have pricing power on repairs, can charge whatever they want for their self driving solutions etc. There's a reason why almost all of them are trying to turn their cars from mechanical vehicles into glorified software/service platforms, it's a way to lock people in.
In a world where hardware and software is open and interoperable and you can say, buy a self driving solution from any vendor (which is essentially what comma does in a hacky way), consumers benefit. Same is true for phones or laptops.
Fine then apply rules equally, I want to be able to use Nissan parts in my BMW and play Xbox and Steam games on my PlayStation…
There are advantages to having a walled garden and I would want to have some assurance that I would be able to block side loading and that it would never be applied without it being clearly and constantly visible to the user. I also want to be sure that no 3rd party can compel me to install their own App Store to get their app which is a quite possible and likely scenario due to the DMA.
In a world where hardware and software is open and interoperable and you can say, buy a self driving solution from any vendor (which is essentially what comma does in a hacky way), consumers benefit. Same is true for phones or laptops.