Cost, maybe? It is one thing to ship up a valuable satellite (which they all can do). But to ship up 1000s of satellites (and keep doing it in perpetuity, because IIRC they don't have a long lifetime[0]) gets expensive.
0: Looks like 5 years. https://www.space.com/spacex-starlink-satellites.html
Because the Chinese govt doesn’t have money to burn…
Another major detail is that SpaceX is simply burning enormous amounts of money on this.
Starlink's revenue is comparable to the ESA's entire 5 billion euro budget, and it still looks like starlink is not net-profitable as a service. (And kessler syndrome avoidance is already pushing up costs with the lower orbits)
The chief problem "stopping" other countries from developing a starlink competitor is that starlink simply doesn't make all that much sense if your country is capable of basic infrastructure construction. Fiber runs are expensive but not that expensive.