- There is no single Play Store equivalent, so the barrier to make people install a relatively unknown app is higher.
- Phones do not come with Google Services Framework, so the barrier to develop a networked app is higher.
- Just like everywhere else, people will use whatever is available because a suboptimal solution is still better than opting out completely from the benefits these solutions bring.
I don't think in China specifically it's about low-end devices or data cost at all. South East Asia - perhaps, but all in all the situation reflects the structure of the economies (the prevalence of monopolistic conglomerates with a finger in every pie).
Most of the time the most widespread solution is far from excellent because it only has to be better than the competition. Even more so when competition is limited by entry barriers to the point it hardly exists. So while the article is a good summary of the situation, it ends up being a bit like wondering why people use Windows.
Android is already one abstraction layer on top of another, there is no intrinsic technological benefit of adding yet another one OS-like super app on top of it, or at the very least any such benefits remain to be demonstrated.