Presently, users are able to create an account without an email address. There isn't text encouraging users to add their email address when creating an account or why it is important. Our intention is to inform users why they should provide their email on Special:CreateAccount.
If a user is creating an account they will see text near the box to input their email address that explains the benefits of adding their email address.
Add some assistive text below the email field explaining the benefit of adding an email address. (Propose using the same text and placement as T194420).