Being able to do payments without a bank through whatsapp is way beyond the risk appetitte of european regulators for example.

Plus forcing whatsapp to add e2e encryption already fixes most of the issues in terms of risk to privacy regardless of how big the userbase it.

That claim does not ring true to me. Maybe a few years ago, but now? I don't use whatsapp and I don't know anyone who uses it, except for a group of expats from South America who probably use it because it's still widespread in South America and their friends use it, maybe?