How do you verify the password meets certain requirements sever side without getting that user data? Client side input can't always be trusted as anyone can modify that regex check.
Here's a project doing passport verification for services without needing to send them a photo of your passport: https://github.com/zk-passport/openpassport
With something like TLS notary you can prove anything signed by a https certificate, so you can prove there are enough funds in your bank to get a mortgage without revealing how much money you have.