Ben Thompson has an in-depth interview with Rivian CEO RJ Scaringe at Stratechery. It has, I think, the best discussion I've come across about Rivian's decision and rationale behind not implementing CarPlay in their vehicles.

This might play out to be the right answer in the long term, but in the short to medium term, until AI assistants and agents are connecting all of our data instead of our phones doing it, it's just friction. I wonder how many Rivian (and Tesla) owners have their phones mounted to their beautiful dashboards? Even in the long term, do we want a different assistant in our Rivian than we use everywhere else in our lives? Worse, do we want a different one in each of our cars and other devices, all acting differently? I say no: our cars should be a source of data for our assistants/agents, not the other way around.

Regardless, this was a worthwhile read.