China has not much left to invest in itself. Their infra is just insanely overbuilt - just search all the massive highways that head out to remote areas, all the solar plants covering deserted areas. They're investing heavily in other countries as well, but many places prefer to invest in themselves. Tech tends to have very high ROI. There's probably lower ROI things like agriculture that are fully invested into.
Subsidies are actually good for the economy. If you invest a few billions into electronics, that allows higher salaries for electronics engineers. The higher salaries mean that people will do electronics in university, and it pays back in a few years.
I feel like some countries avoid them for cultural reasons. Partly because it could be seen as a form of corruption - chicken farm XYZ pays $100m to support both parties during the election, and suddenly there are $10B in subsidies for chicken farms after the election regardless of who wins. Most countries have more than two parties, so this can also get expensive. China has only one.
Some places have the bubble problem - electronics salaries are too high, and further subsidization increases the salaries past sustainable values, which may also increase the cost and price of the products.
Some subsidies are more subtle, e.g. a lot of US tech is indirectly subsidized via military contracts, which also does the work of filtering corruption.