There appears to be (at least) two inter-related forces contributing to this effect. First, there are simply too many people. Even a small city such as Fuyang (where my dad's family resides) has a population of over two million. Despite China seeming like a large country geographically, most of the western regions are uninhabited. As a result, most of the 1.4 billion Chinese folk are crammed along the eastern seaboard.
A second related reason seems to be cultural. Many people seemed to be used to (or resigned to) the idea of the public areas being under-maintained. For example, my aunt's housing complex in Beijing looks a little rundown from the outside. Litter is strewn about the parkway, the main corridors look like unfinished, and the elevator seems like on the verge of breaking down. But her actual home is a nice and tidy two bedroom unit. I asked my aunt why no one bothered to renovate at least the main corridors (imagine the front lobby of a condo building in Chicago being rundown/unfinished but the individual units are nicely finished). She replied that not only does there not exist an organization responsible for such projects, no one really cares enough to pay more for the upkeep of these more public areas.
Robin Hanson recently wrote a blog post describing what he defines at the two key disputed values in any given society. One point he makes is particularly relevant here,
Cultures where invasion was less an issue tended to evolve family oriented values, while cultures where invasion was more common focused more on larger community solidarity.Certainly, China has experienced relatively few external invasions in its history, and I know from personal experience that the country is very family oriented. And given the huge concentration of people (both rich and poor) living in the same area, the forced mixing of the populations might necessarily encourage people to be more limited in their domain of care.
For example, even if these housing complexes in Beijing were well maintained from head to toe, most of its inhabitants would still have to pass through less savory parts of the city during their daily excursions. So it's not that big a difference said less savory parts extended a little closer to home. It's a little reminiscent of nice university communities surrounded by less affluent neighborhoods (e.g., Yale and UChicago), albeit to a much larger degree.
But of course, there are some things that are universal across all cultures. Cute toddlers, for instance.