Also, shutting down these markets would be very difficult, as many people depend on it and they proprietors of these markets take measures against being caught. It would be about the same level of difficulty as shutting down a drug dealer in the US.To be fair there are a few things here. Number one, China is extremely densely populated whilst also having very close proximity to wildlife.
Whilst China is not the only country that has wet markets they are very plentiful and the key point is that they are mostly in very densely populated places. China is one of the few countries that has wet markets say 50 meters away from 5 star hotels or office buildings for example. This does mean that the jump is easier.
Historically China has also been the source for many diseases in the past again due to the abundance of wildlife within a close proximity to a huge amount of people. The fact that China is so verdant and so crowded makes it the perfect breeding ground for this.
Also, the wet markets in China are more unhygienic than any I have seen even compared to Africa where the population density is much lower in general. This lack of hygiene does mean that exposures are much higher potentially.