Because a low and high cost phone do essentially the same thing, whereas a high trim car will do things like steering assistance in a way the low trim does not

Because a low and high cost phone do essentially the same thing, whereas a high trim car will do things like steering assistance in a way the low trim does not do at all. And to support the differences high trim will have different sensors and differently distributed compute. This means that the infotainment system will be running in different places on different cars.