'Back in the day' Apple was dependent on its computer sales. Today, not so much. They'll never let iOS out of the bag, but macOS isn't their Sugar Daddy an more, nor are non-iMac/non-laptop computer sales.
I'm saying that the AIO (and the laptop) are the only computers Apple cares about, basically the computer-as-appliance market. Apple clearly doesn't worry about the users who want freedom from the AIO computer, or care for that matter. The best face to be put on it is that Apple does not care what this particular user class wants or needs, and is also unwilling to provide them a way (other than the Hackintosh route, which they do little to support) to get what they need from elsewhere in order to protect their bottom line. I see this as very short-sighted, but that appears to be where Apple is these days.