>But [CarPlay] could also be #4 "Preventing people who are subscribing to your thing from switching to somebody else's thing."

The more reasons an existing user has to value something they already use, the harder it becomes for the user to switch. With few points of stickiness, it's easy for a user to check if an alternative has, say, similarities to features A and B. But if it's ABCDEFGHIJK, the likelihood of that user leaving drops dramatically. It's a common point that Apple does well iterating on its products, but that iteration goes beyond performance and capabilities into areas of stickiness.