This is because fax is still considered by HIPAA to be a secure method of transferring patient information. Where email is unencrypted and this considered to be insecure.
[UK's] NHS world's biggest fax machine buyer due to 'stubborn' resistance to new technology, say medical leaders
There are jurisdictions outside of the US that transmit health records by fax to avoid them being subject to the USA PATRIOT Act when they transit routers in the United States.
Seems like you could fax an encrypted payload and just use the fax protocol for data transmission.
Possibly even attach it to another medium originally intended for data.
Also, I love your username in the context of this subthread.