This is a silly reason to hold back if that was their plan. You can buy, for $20 and up, little USB-sticks that allow wired-CarPlay cars to do wireless CarPlay. Apple could manufacture 100 million of those, at a cost of $5 for the boards and maybe $8 in glass and aluminum, and sell them at a huge profit for $79.99 and advertise them as a revolutionary breakthrough they invented.

Wired CarPlay is not holding Apple back. I think they just figure it’d be harder for them to repair partially-bricked iPhones if they had no port to do DFU or whatever. That or they actually have done the market research and customers said they’d hold off on buying a portless iPhone because it’s a stupid idea.