Actually, that’s not completely true. You’re not automatically given a free iCloud email. When you register/sign up for your first Apple ID you're asked to put in an email address which can be anything you’d like as gmail, and that is that... but if you want to then you can alternatively choose to create an icloud email instead of using an existing email of your choice.. I had my gmail for almost a decade until I was stupid enough to take the offer to create an iCloud email for my Apple ID, and that’s how I got stuck with it as an alias after switching back to gmail as my primary email