All of them.

My personal tax agent only accepts forms and sends them back via email. I had a conversation with him about using password protected zips and he just told me he won't accept them.

My hospital sent me a PDF that I was to fill in and email back with cleartext credit card information filled in to pay bills. Screenshot:

https://infosec.exchange/@jsmall/116745959468132388

I recently deal with an inheritance and the Super Fund would only accept legal documents by email. I could go on, this is normal.