[toyg]

Every year, new tablets and/or phones have to be ready for Black Monday and Christmas.

Every year, the phone OS has to keep up with new tablets and/or phones.

Every year, the laptop OS has to keep up with the phone OS.

That's basically it. At Apple, where the phone goes, everything else follows.

[p_l]

And for image reasons, it must be "major" release instead of minor release for hw support (like many commercial OSes did in the past, I think even macOS)