They are sometimes required. Say you are on a mailing list for some company you gave your email to at some checkout counter one time, and you want to unsubscribe. You probably don't have an actual account with a login with that retailer, they just have your email address.
In this case, what alternative is there than having a magic link in the footer of that email that says "unsubscribe" that includes a token unique to that email address that acts as proof of owning an email account when you then click that link and ask to unsubscribe?
In this case, what alternative is there than having a magic link in the footer of that email that says "unsubscribe" that includes a token unique to that email address that acts as proof of owning an email account when you then click that link and ask to unsubscribe?