Wechat has no ads because the government uses it to spy on almost everything you are doing from paying a parking ticket to purchasing groceries. It has replaced cash in many areas of China.
It's also tightly controlled and censored.
I would much rather have advertisers trying to sell me something than a totalitarian government using it to control my life.
Fair enough, but also keep in mind that what constitutes a crime changes over time and culture. The law is also vulnerable to interpretation, for better or for worse, by those who enforce it.
