and wechat is indeed in the center of this system. For example, a fruit stand would now accept mobile payment via wechat. those who run fruit stands are usually farmers.
I think it makes a lot of sense to build mobile payment into a a social app. because any currency would require a social network. and transferring money is a key social activity.
building independent mobile payment without the support from a mature social network is a bad idea, for example square and apple pay (only useable in the apple ecosystem, a partial mobile ecosystem).
China never seemed to have a credit card era, it jumped directly from paying cash to paying with mobile. whereas in the U.S., credit card is so convenient, people don't want to change.
for many years, wechat has been combining new features with its social network, whereas whatsapp wanted to be a pure chatting app and missed many opportunities.
you can use wechat to order food at restaurants, you can log into public wifi with wechat ....
This is just one example. Another thing I noticed is online shopping. At the gate of our apartment, each day, there are many deliver guys on tricycles. They have a more efficient and cheap delivering system.
For example, in the yard of our apartment we have storage cabinets with password locks. The deliver guys won't deliver each package to your door, as it is inefficient, especially because apartment buildings are tall in China, you have to take elevator. Instead, they put packages into one of the cabinet doors. And you will receive a password on your phone. Put the code in, the cabinet door will open. you can then get the package.
This is not a complex idea, but hard to implement in the U.S., because we don't have the same population density here. When you build an infrastructure like this, you want to serve as many people as possible.