[wpm]

Sure, but I get my OS upgrades from the System Settings app now, what was stopping me from doing that in the early 2010s?

And yes, the Mac App Store was brand new, what better way to boost engagement than to move a fairly standard and typical function into it even though it was unrelated? Sounds like a good way to trick people into using your new thing. Like a boost, to engagement, one could say.

[wtallis]

The blocker was that they were still charging money for new OS versions at that time. System Preferences didn't have a payment processing system, the App Store did.