Nobody wants to live in a developing country. It is therefore subpar.
Being the country with the most recently constructed industries has a benefit, too, and that benefit frequently comes from being an underdeveloped country. For instance, the majority of the steel plants in the United States were constructed before the start of World War II, while South Korea's steel sector was developed decades later. The Korean steel plants were more cost-effective and able to undercut the price of American steel because they made use of new technologies. U.S. steel plants eventually had to shut down due to their lack of competitiveness.
Similar to this, China had a cost advantage due to its cheap wages because it was undeveloped when it opened up to the global market under Deng. In recent years, as its economy has grown, its wages have increased.