What makes you think they don't include the price of the OS when you buy their hardware? In fact, that's how many justify paying a higher price for Apple produc

What makes you think they don't include the price of the OS when you buy their hardware? In fact, that's how many justify paying a higher price for Apple products - you get macOS, Pages / Numbers / Keynote, iMessage / Facetime etc. That's also why they stop supporting old hardwares after a period.