Twitter doesn't have any method to fetch the user's email address. Because of that, the user has to go through a registration process to ask their email address. You can disable all other fields on the registration form, like name, username and password, but the user needs to add their email address for a Joomla account to be created for them.
I hope that helps explain, but if you have any other questions, just let me know.
Thanks,
Alex
twitter log in
