Further, and this is purely conjecture, it is possible their lawyers considered the alternative of email but decided it was too risky for reasons of uncertainty

Further, and this is purely conjecture, it is possible their lawyers considered the alternative of email but decided it was too risky for reasons of uncertainty of message delivery/receipt. I can imagine being an engineer in a room of lawyers and having them ask me how can I ensure that all customers see the message. I would say that's not possible, but there are ways to maximize the likelihood it will be seen.