Apple collects no money from Steam sales, so they don't see a reason to support it.

You don't buy Apple to use your computer they way you want to use it. You buy it to use it the way they tell you to. E.g. "you're holding it wrong" fiasco.

In some ways this is good for general consumers (and even developers, with limited config comes less unpredictablilty)... However this generally is bad for power users or "niche" users like Mac gamers.