This is part of the same reason many people don't use Bitcoin- you can't actually do much with it because retailers don't accept it. But China is definitely thinking about how to fix that problem, and soon they will make it possible to pay directly in CNY in other countries. Once you can buy things with it, the CNY is attractive from a practical perspective. A lot of your stuff is already manufactured in China, once/if using CNY makes your purchase easier then it's going to gain ground on the USD.
https://www.atlanticcouncil.org/blogs/econographics/what-to-...