Not just that, China has super apps that integrate everything from payments, food delivery, taxi, social media... To single application. Integrating this app directly into OS as a launcher (or shell) kind of makes sense.
("third party" and "private" parts are relevant, IMO, otherwise Twitter superapp-ification had happened years ago)
My point is that 3td party apps do not make much sense in China. They are useless without support from super app
There are Chinese regional apk distribution sites for Chinese phones. You don't hear about those(I don't either) because there are near zero communication bandwidth across languages on this planet. That doesn't mean they don't exist.
I mean, you're simply describing an operating system. The west builds this as an operating system. China builds it as an app. The rise of the Chinese super-apps is literally just a response to the reality that the West, especially Apple, forces everyone they work with to think inside the App box. Uber has to build an app if they want to access Apple's customers; but with the Uber app adding delivery, its also becoming a little Super.
The more interesting question is why the west doesn't have super-apps similar to the east. The reality, which I hinted to, is that I think we're starting to see more of them; Uber has delivery, Spotify is adding audiobooks, Google is adding an AI assistant, I think the scope-creep of these apps should give you a clue as to why China built them first.
There's certainly cultural aesthetic differences; maybe the west places greater importance on simplicity and focus. I think the bigger reason is market dynamics. The west has a relatively far more competitive market among these goods and services providers. The primary fuel funding technology companies over the past twenty years has been venture capital, which is attracted to younger, newer companies over the old established players. But, venture capital is slowing down, the marketplace is calcifying a bit among the established players, both new ones from the VC boom and old ones which survived it: And now we're starting to see these players branch out from their core competency and become more-and-more super-appy as they pursue greater growth with less fear that a startup is going to drive-by and eat their lunch.
That and he just has a kooky fascination with the letter X.
But not that it matters in the end considering the chaos the US has where eventually everyone gets to see what we do on our cells to. It is just a matter of speed, China is probably just more efficient.