Not so much a technical requirement as a business requirement.
One time I was working for a design company that was building a website for a local business owner. We were building a website that included online shopping (e-commerce), but a requirement of doing business with this owner was that all our communication had to be hand-written and delivered in person.
I guess talking about the design details of the website over email was too risky in some way… but it doesn't make sense to me that somebody who refuses to email because of lack of security when talking about non-confidential things would build a website where they would ask shoppers to enter their payment details.
Either way, I remember being at the office when a new stack of hand-written notes for website content was delivered and we all stopped what we were doing to type up the written notes so we could put the content on the website.