The signup form could have only 2 fields, too: Username and Password. You don't need to demand an email address if your site can give some functionality that do

The signup form could have only 2 fields, too: Username and Password. You don't need to demand an email address if your site can give some functionality that doesn't require interacting with others. You could make it so that a username is only "called out" once the email address is confirmed. So nobody can register all desirable names just to prevent others from having it (and of course have some throttling of registrations).