Ok, this one is entirely fair, but also I'd argue the circumstances around it are a little different.
Given how tightly integrated wechat is with the chinese government, and the restriction of wechat pay to use with folks who have a Chinese/Hong Kong bank account, we're talking about different levels of utility around preserving the record.
If the government chooses not to honor your transaction record, it doesn't really matter if you have a copy yourself.
You can do pretty much anything you want in WeChat, and you don't need an email.