That would be like you buying something at the dollar store.
At some point the ongoing maintenance and support as well as coordination and organizational distraction mean it wouldn't get approved if internal engineers offered to start it off for free.
They're avoiding it because installing Linux (or Windows, even), would actually decrease their income. I doubt people running Windows on Intel Macs were avid Apple Music subscribers.
or are you saying apple devices are loss-leader prior the app store revenue ?
that's the model taken to the extreme
It's fairly clear which direction the wind is blowing.
Also, hardware - software integration pushes more hardware sales. People with iPhones are a lot more likely to buy Macs than people with Android phones. Same story for Airpods & co. I've also basically never seen an Apple keyboard used with non-Apple computers.