Because FIFA stipulates that the member associations that bid for the World Cup must be associations on all continents except the countries (or regions) that have hosted the last two World Cups. As the United States, Canada, Mexico and Qatar will host the 2026 and 2022 World Cups respectively, according to the rules, North America and Asia can no longer bid for the 2030 World Cup. If China wants to host the World Cup, it can only wait until 2034, because Asia can bid for this World Cup without any restrictions.
Of course, as far as the current situation is concerned, China still has a chance to bid for the 2030 World Cup. When FIFA voted for the host city of the 2030 World Cup at the General Assembly, the voting was inconclusive, that is, no national or regional association could get the required votes at the General Assembly. In this case, FIFA will start the second round of bidding, and at this time, other Asian member associations including China Football Association, where Qatar, the host of the 2022 World Cup, is located, can participate in the bidding.
It is precisely because many countries on all continents have made it clear that they will bid for the 2030 World Cup, so it is not easy for China to stand out from so many countries. Besides, China has not made it clear that it will bid for the 2030 World Cup.
There is also a big gap between the football level in China and the World Cup. We need a long time to lay the foundation and select better players to ensure that our own strength can be comparable to that of the World Cup.