Building a self-driving car is vastly more complex and comes with a lot more regulatory problems than building a competitor to the Nomad. Also, Apple has had trouble recruiting top AI talent, among other reasons due to their secrecy in a field where publishing is everything. Though, they have opened up a bit.
I am not saying it can't be done. But Apple has been quite bad at machine learning so far.
I don't think that they are bad, just that their focus is more on the product holistically than as a standout feature. i.e. machine learning is a means to an end, not the end in itself. Whereas Google, Amazon etc sells products and services like GCP, AWS Recognition etc. Naturally they would like to market themselves as being the experts, and have the credentialed professionals to do so.
I am not saying it can't be done. But Apple has been quite bad at machine learning so far.