Why do people send text messages and add WeChat at night?

The high probability has no effect. If the other party will be an insurance salesman, an advertising agent, a real estate agent, or even the answers to some test questions, such people may have bought your communication information from others. These people want to add you to WeChat, maybe they want to sell their goods to you. Of course, it doesn't rule out that some friends who haven't contacted for a long time suddenly come to you and want to contact you. Well, some of them are frauds. If there is fraud, you'd better not answer the phone.