According to Car and Driver, via a BMW representative, it boils down to the fact that it requires engineering and testing to make CarPlay work, and then keep working. The development phase is just one aspect, and then when there's an update to CarPlay's code, whether it's a bug fix or new feature, there's a chance "that some new snippet of code won't play nice with the existing infotainment system, requiring an update; wireless CarPlay increases that complexity."

This does sound fair enough until you consider the cost, and we all know the result of technology not getting updated and the frustration of having to live with bugs. There's also the security aspect to consider, and as technology becomes more complex in cars, after-sales support is a relatively new problem that automakers face. We are also starting to live in a subscription world.